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  1. ·machine learning

    Google and Kaggle Gen AI study notes — the opening foundations

    An opening-reading notebook, not a completed five-day course: distinguish recurrence, attention, autoregressive generation, prompting, retrieval and fine-tuning.

    8 min read
  2. ·data engineering

    Apache Airflow - open source orchestration engine

    Design retry-safe Airflow tasks without mistaking DAG ordering for a database transaction. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    19 min read
  3. ·machine learning

    Applied LLMs — origins, evidence and applications

    A readable route through LLM foundations, attention, retrieval, prompting, audio, clinical NLP, statistical learning and deployment responsibilities.

    12 min read
  4. ·algorithms

    Variant contracts: bounded budgets, interval cuts and subset routes

    Extend the restored problem-family series with bounded knapsack, two resource budgets, interval reconstruction and Held–Karp routes, using independent tiny oracles.

    30 min read
  5. ·data engineering

    Data Infrastructure for AI and Experimentation at Scale

    Trace events, time-valid features, recommendation decisions and experiment outcomes through a source-reviewed data platform with executable SQL and statistical fixtures.

    55 min read
  6. ·data engineering

    Data Platform & Orchestration

    A data platform is a chain of independently testable contracts. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    8 min read
  7. ·machine learning

    Deep Learning and LLMs: an inspectable learning laboratory

    A broad deep-learning and LLM progression with a verified NumPy spine, advanced framework and systems lessons, source evidence and explicit execution boundaries.

    13 min read
  8. ·systems

    Recommendation quality starts before ranking

    An executable retrieve-score-rerank pipeline that exposes candidate recall and diversity trade-offs.

    11 min read
  9. ·systems

    Designing for Scale · Requirements to Architecture

    Convert prompts into testable requirements, capacity constraints and failure contracts through four worked designs and a traceable review method.

    24 min read
  10. ·systems

    Capacity estimates that survive an overload question

    Derive traffic, storage, bandwidth, working set and backlog with explicit units, sensitivity analysis and exact retained laboratory programs.

    22 min read
  11. ·systems

    Designing for Scale · The Storage Decision Tree

    Storage selection has several independent axes. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    8 min read
  12. ·systems

    Designing for Scale · CAP and the Consistency Spectrum

    CAP is a history argument, not a database label. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    9 min read
  13. ·systems

    Designing for Scale · URL Shortener

    Identifier probability and redirect policy. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    9 min read
  14. ·systems

    Token buckets: bursts, clocks and the atomic boundary

    Implement and test one token bucket, then identify what changes when several servers enforce the same quota.

    12 min read
  15. ·systems

    Designing for Scale · Chat and Real-time Communication

    Transport, durable acceptance and per-conversation order. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    9 min read
  16. ·systems

    Designing for Scale · Newsfeed and Fan-out

    Hybrid fan-out is a workload decision, not a law. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    8 min read
  17. ·systems

    Designing for Scale · Typeahead and Search Autocomplete

    Prefix lookup, top-k maintenance and hot prefixes. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    9 min read
  18. ·systems

    Designing for Scale · Notification Systems

    The provider acknowledgement is an uncertainty boundary. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    9 min read
  19. ·data engineering

    Designing for Scale · Real-Time Analytics

    Provisional and final aggregates must agree on ownership. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    9 min read
  20. ·data engineering

    Designing for Scale · Change Data Capture (CDC)

    Build CDC and transactional-outbox reasoning around coordinated snapshots, durable intent, replay identity, schema evolution and WAL retention.

    12 min read
  21. ·data engineering

    Designing for Scale · The Data Lakehouse

    Explain atomic table snapshots over immutable files, writer conflicts, row deletes, schema identity, maintenance and measured architecture trade-offs.

    12 min read
  22. ·systems

    A metering ledger that survives a replay

    Put event identity and usage aggregation in one transaction, then test rollback, duplicates and conflicting payloads.

    12 min read
  23. ·systems

    Historical features need two clocks

    A point-in-time join lab that rejects future events and late backfills while preserving explicit TTL semantics.

    12 min read
  24. ·systems

    Designing for Scale · Model Serving

    Budget model-serving queues, batching, memory and asymmetric scaling, then design bounded shadow deployments and controlled rollouts.

    22 min read
  25. ·systems

    Designing for Scale · RAG and Vector Search

    Build versioned authorized retrieval, compare exact and approximate search, fuse lexical and vector candidates, and test evidence boundaries.

    24 min read
  26. ·systems

    Release gates need denominators, not reassuring scores

    Combine deterministic checks, calibrated model judges, multimodal evidence and statistically explicit release gates without replacing human accountability.

    24 min read
  27. ·systems

    Designing for Scale · End-to-End Design Review I

    Trace video upload, processing, publication, feed fanout and deletion through a worked capacity model and guarded state machine.

    24 min read
  28. ·systems

    Designing for Scale · End-to-End Design Review II

    Protect ticket inventory through bounded admission, short transactions, durable holds and idempotent payment reconciliation with a SQLite state-machine fixture.

    27 min read
  29. ·systems

    Systems laboratory: make the failure observable

    A practical route from capacity estimates to replay-safe data, permission-aware retrieval and evidence-based release gates.

    11 min read
  30. ·machine learning

    A deep-study prompt with examples, evidence and an audio version

    Build a bounded study request, keep sources separate from narration, and evaluate generated explanations instead of mistaking fluent detail for verified knowledge.

    10 min read
  31. ·data engineering

    Overall Engineering Clarity — Data, Distributed Systems and AI (Deep Dive)

    Trace compute, commit, indexing and authorization boundaries across a data/AI platform. Mechanisms, worked examples, failure analysis and complete practice answers.

    119 min read
  32. ·machine learning

    How transformers actually attend — a weighted lookup you can calculate

    Follow queries, keys and values through a numeric attention head, test causal masking, and separate multi-head capacity from guaranteed interpretability or long-context quality.

    12 min read
  33. ·machine learning

    Image classification: from a scalar model to a tested experiment contract

    Derive loss and softmax, plan controlled Fashion-MNIST experiments, and follow complete local TensorFlow references for training, callbacks and save/load.

    30 min read
  34. ·systems

    Replay is a feature; duplicate effects are a design choice

    Choose partition keys and independent groups for hot, warm and cold ML pipelines. Mechanisms, worked examples, failure analysis and complete practice answers.

    12 min read
  35. ·systems

    Kimi K3: architecture, derivations and a pinned-source audit

    Derive KDA state updates, depth attention and latent expert routing; reconcile pinned Kimi architecture claims and execution limits.

    56 min read
  36. ·algorithms

    01 · Programs as contracts: values, state and tests

    Build a small event normalizer, expose aliasing, and distinguish a test from a proof. Python foundations without a catalogue of syntax.

    14 min read
  37. ·algorithms

    02 · Count work, then remember what matters

    Derive hash counting and prefix sums from repeated work, with brute-force oracles and honest complexity assumptions.

    13 min read
  38. ·algorithms

    03 · Discarding possibilities: search and windows

    Prove which candidates can be discarded, derive lower bound, and see exactly why negative numbers break a common window.

    14 min read
  39. ·algorithms

    04 · Unfinished work: stacks, queues and heaps

    Choose a removal policy, prove a next-greater stack, and maintain a bounded top-k heap without confusing partial order with sorting.

    13 min read
  40. ·algorithms

    05 · Graphs: reachable is not ready

    Derive unweighted shortest paths and dependency ordering, with explicit edge direction, cycle rejection and bounded exhaustive tests.

    16 min read
  41. ·algorithms

    06 · Dynamic programming: choose a sufficient state

    Derive take-or-skip recurrence, explain backward capacity updates, and distinguish exact amounts, capacity bounds and counting order.

    16 min read
  42. ·systems

    07 · Relations, joins and all-or-nothing changes

    Build an in-memory SQLite notebook, preserve zero-event jobs in a join, and test rollback without confusing it with crash durability.

    15 min read
  43. ·systems

    08 · Retries: a timeout is not a verdict

    Model a lost acknowledgement, define idempotent effects, and separate delivery, durable processing and response replay.

    13 min read
  44. ·systems

    09 · Bounded work: queues, deadlines and ownership

    Reason about backlog growth, choose an overload policy and distinguish admission, completion and cancellation without running a server.

    12 min read
  45. ·systems

    10 · Capstone: a trustworthy local job notebook

    Integrate validation, dependency checks, atomic event ingestion and retry tests. A runnable reference core and an evidence-based assessment rubric.

    19 min read
  46. ·systems

    Capstone: an evidence service with replay-safe usage

    Compose tenant-scoped retrieval, explicit abstention and a durable-event invariant into one executable failure lab.

    6 min read
  47. ·learning

    Building a Learning System That Actually Sticks

    Research-informed retrieval and spacing with a broad curriculum, honest schedule arithmetic, bounded review queues and no invented automation or mastery promises.

    30 min read
  48. ·algorithms

    The LeetCode Game — How to Read a Problem

    Constraints are not decoration. They are a reviewer quietly telling you which complexity class is acceptable, and therefore which algorithm to reach for.

    19 min read
  49. ·algorithms

    Big-O in Practice — Counting, Not Vibes

    How to derive the cost of a Python data structure operation from how it is built, instead of memorising a table you half-remember under pressure.

    16 min read
  50. ·algorithms

    Python for Speed — The 20 Idioms That Matter

    The small set of standard-library tools that turn a fifteen-line design review solution into a five-line one, and the syntax you must be able to type without thinking.

    15 min read
  51. ·algorithms

    Arrays & Strings — In-Place Discipline

    The read pointer and write pointer skeleton that solves a surprising share of Easy problems, and the index bookkeeping that makes it correct on the first try.

    17 min read
  52. ·algorithms

    Hashing — Your Default Weapon

    The complement-lookup skeleton and the general move of trading memory for time, which is the first thing to try whenever a problem looks quadratic.

    16 min read
  53. ·algorithms

    UMPIRE — The Problem-Solving Framework

    A six-step process for the twenty minutes between reading a problem and having working code, so that being stuck becomes a step rather than a state.

    18 min read
  54. ·algorithms

    Two Pointers I — Opposite Ends

    Two indices converging from the ends of a sorted array, and the monotonicity argument that proves you can discard a whole row of candidates with one comparison.

    24 min read
  55. ·algorithms

    Two Pointers II — Same Direction & Fast-Slow

    Two pointers moving the same way at different speeds: the read/write compaction you already know, and Floyd's cycle detection, which finds a loop in O(1) memory.

    18 min read
  56. ·algorithms

    Sliding Window I — Fixed Size

    Maintaining a window aggregate incrementally so that sliding costs O(1) instead of O(k), which turns the obvious O(n*k) scan into a single pass.

    14 min read
  57. ·algorithms

    Sliding Window II — Variable Size

    Expand right unconditionally, shrink left while the invariant is broken, record at the right moment — and the amortisation argument that keeps it linear.

    15 min read
  58. ·algorithms

    Sliding Window III — With Counts

    Windows whose validity depends on a frequency map, and the single integer counter that lets you test that condition in O(1) instead of rescanning the map.

    17 min read
  59. ·algorithms

    Prefix Sums & Difference Arrays

    Precomputing cumulative sums to answer range queries in O(1), and the prefix-plus-hashmap combination that counts subarrays where sliding windows are unsound.

    16 min read
  60. ·algorithms

    Binary Search I — The Template

    One binary search template with a half-open invariant that never loops forever and never goes off by one, and the discipline of owning exactly one version of it.

    16 min read
  61. ·algorithms

    Binary Search II — Rotated & 2D

    Binary search when the array is no longer sorted end-to-end: decide which half is still sorted, then discard the other. Same trick flattens a 2D matrix into one index space.

    17 min read
  62. ·algorithms

    Binary Search III — On the Answer

    Stop searching the array and start searching the answer range: define a monotonic feasibility predicate, then binary search the smallest x for which it holds.

    17 min read
  63. ·algorithms

    Stacks — LIFO & Matching

    Nesting, matching, undo and expression evaluation are one idea: push what you expect, pop when it arrives, and carry auxiliary state alongside for O(1) queries like min.

    19 min read
  64. ·algorithms

    Monotonic Stack

    Next greater and next smaller element in O(n): keep a stack whose order never breaks, and pop everything the current element resolves.

    23 min read
  65. ·algorithms

    Queues & Monotonic Deques

    The queue as BFS substrate, and the monotonic deque that answers sliding-window maximum in O(n) by discarding candidates that can never win again.

    25 min read
  66. ·algorithms

    Linked Lists I — Traversal & Reversal

    The dummy head that deletes most linked-list edge cases, and the prev/cur/next three-step reversal you should be able to write without thinking.

    20 min read
  67. ·algorithms

    Linked Lists II — Cycles, Middle, Reorder

    Floyd's tortoise and hare for cycle detection and entry point, finding the middle in one pass, and composing split-reverse-merge to reorder a list in O(1) space.

    20 min read
  68. ·algorithms

    Recursion & the Call Stack

    Base case discipline, hand-tracing a call stack, and knowing when recursion is the wrong tool — the substrate under trees, backtracking and dynamic programming.

    18 min read
  69. ·algorithms

    Trees I — DFS Traversals

    Preorder, inorder and postorder as one recursive skeleton with the work line moved, plus the iterative forms and when they are worth writing.

    19 min read
  70. ·algorithms

    Trees II — BFS / Level Order

    Snapshot the queue length at the top of each iteration and you have level-order traversal — the one trick behind right side view, zigzag, and minimum depth.

    19 min read
  71. ·algorithms

    Trees III — BST Properties

    Two views of a binary search tree: inorder traversal yields sorted order, and validation requires passing bounds down rather than comparing parent to child.

    21 min read
  72. ·algorithms

    Trees IV — Paths & Accumulators

    The return-one-thing-track-another pattern: a recursion whose return value serves the parent while a separate accumulator records the global best.

    21 min read
  73. ·algorithms

    Heaps & Top-K

    When a problem asks for the K largest, K smallest, or K most frequent of anything, you almost never need to sort. A size-K heap answers it in O(n log k).

    20 min read
  74. ·algorithms

    Graphs I — Representation & DFS

    Build the adjacency list, carry a visited set, and recognise that a grid is already a graph — then count connected components with a depth-first sweep.

    23 min read
  75. ·algorithms

    Graphs II — BFS & Shortest Path

    Breadth-first search level by level, why it gives shortest paths in unweighted graphs, and the multi-source variant that solves nearest-X grid problems in one sweep.

    19 min read
  76. ·algorithms

    Graphs III — Topological Sort

    Kahn's in-degree algorithm for ordering tasks with dependencies, and why a queue that empties early is exactly a cycle detector.

    18 min read
  77. ·algorithms

    Graphs IV — Union-Find (DSU)

    Fifteen lines of disjoint-set union with path compression and union by rank, and the family of connectivity problems it collapses into near-constant time.

    18 min read
  78. ·algorithms

    Backtracking I — Subsets & Combinations

    One choose-explore-unchoose template that generates subsets, combinations and permutations, plus the two ways to skip duplicates without producing duplicate output.

    19 min read
  79. ·algorithms

    Backtracking II — Constraint Grids

    Pruning before you recurse, restoring board state exactly, and the O(1) validity checks that turn N-Queens and Sudoku from intractable into instant.

    21 min read
  80. ·algorithms

    DP I — Recognising Overlapping Subproblems

    DP is recursion plus a cache. Write the recursion, add lru_cache, convert to a table — mechanically, in that order, every time.

    25 min read
  81. ·algorithms

    DP II — 1D Linear

    Define dp[i] in English before you write code. The House Robber family, and why most DP bugs are undefined state rather than a wrong transition.

    20 min read
  82. ·algorithms

    DP III — Take / Skip Decisions

    The binary-decision DP shape: at each index you either act or you don't. State machines for cooldown, reachability for Jump Game, and split points for Word Break.

    21 min read
  83. ·algorithms

    DP IV — Subsequences (LIS / LCS)

    Longest Increasing Subsequence and Longest Common Subsequence are the two parent problems behind a huge family. Know both cold and most subsequence DP becomes recognition.

    20 min read
  84. ·algorithms

    DP V — 0/1 Knapsack

    Derive the 0/1 knapsack recurrence, prove why compressed capacity updates descend, and adapt the state to partition, sign assignments and reconstruction.

    17 min read
  85. ·algorithms

    DP VI — Unbounded Knapsack

    The knapsack where each item is available in unlimited supply. One character changes from 0/1 — the capacity loop direction — and Coin Change, Rod Cutting, and Combination Sum IV all fall out of it.

    16 min read
  86. ·algorithms

    DP VII — 2D Grid

    Grid DP is the friendliest dynamic programming: each cell is built from the one above and the one to its left. Use it to make DP feel mechanical before string DP.

    19 min read
  87. ·algorithms

    DP VIII — String DP / Edit Distance

    The two-string DP table: dp[i][j] over prefixes, the three-way insert/delete/replace recurrence, and how Distinct Subsequences and Interleaving String are the same table with different transitions.

    21 min read
  88. ·algorithms

    DP IX — Palindromes

    Expand-around-centre versus the 2D palindrome table: two O(n^2) approaches with very different failure rates, and when partitioning forces you back to explicit DP.

    21 min read
  89. ·algorithms

    DP X — Interval DP

    dp[i][j] over ranges with an inner split point k: why Burst Balloons only works when you think about the LAST balloon, and how sentinel padding removes the boundary cases.

    23 min read
  90. ·algorithms

    DP XI — State Machine

    Naming your DP states explicitly: hold and free arrays for the stock problems, why drawing the transition diagram first collapses the difficulty, and how the k-transaction version generalises.

    24 min read
  91. ·algorithms

    DP XII — Bitmask DP

    Encoding a subset as an integer: when n is at most 20 the exponential state is affordable, the standard submask and popcount idioms, and why the constraint tells you before the problem does.

    20 min read
  92. ·algorithms

    Tries — Prefix Trees

    Children dict plus terminal flag: building a trie in ten lines, and why Word Search II is trie-plus-backtracking rather than a dictionary scan.

    20 min read
  93. ·algorithms

    Bit Manipulation

    XOR cancels itself, n & (n-1) clears the lowest set bit, and how to add two integers without the plus operator. The handful of bit tricks that actually recur in practice.

    23 min read
  94. ·algorithms

    Math & Number Theory

    Fast exponentiation by squaring, the sieve of Eratosthenes, Euclid's GCD, and binary search on integers — the four math routines worth memorising outright.

    26 min read
  95. ·algorithms

    Intervals

    Sort by start, merge on overlap: the four-problem interval family, and why Meeting Rooms II needs a heap on top of the sort.

    23 min read
  96. ·algorithms

    Greedy — And Proving It Works

    Greedy feels right and is often wrong. The exchange argument, the counter-example hunt you should run first, and four problems where greedy genuinely is optimal.

    27 min read
  97. ·algorithms

    Matrix Manipulation

    Transpose then reverse to rotate in place, four-boundary control for spiral traversal, and using the first row and column as O(1) marker storage.

    19 min read
  98. ·algorithms

    Design I — Composing for O(1)

    Hashmap plus doubly-linked list for LRU, array plus index map for GetRandom, and the general move of combining two structures so each covers the other's weakness.

    20 min read
  99. ·algorithms

    Design II — Streams & Time

    Two balanced heaps for a running median, binary search over versioned timestamps, and merging k sorted feeds — the design patterns for data that arrives over time.

    27 min read
  100. ·algorithms

    Sorting & Custom Comparators

    Partition-based selection and comparator design: Dutch national flag, quickselect for Kth largest in O(n) average, and cmp_to_key for orderings that are not a simple key.

    23 min read
  101. ·algorithms

    Segment Trees & Fenwick (BIT)

    Range query with point update in O(log n): the recursive segment tree skeleton, the Fenwick tree's low-bit trick, and how to recognise the rare problem that actually needs one.

    20 min read
  102. ·algorithms

    String Algorithms

    KMP's failure function, rolling hashes, and the Z-function — the three ways to avoid re-comparing characters you have already matched.

    19 min read
  103. ·algorithms

    Advanced Graphs

    Dijkstra as BFS with a priority queue, Bellman-Ford for negative weights and bounded hops, and the two minimum spanning tree algorithms — with the cue for choosing between them.

    19 min read
  104. ·algorithms

    Mock Set 1 — Mixed Easy/Medium, 45 min

    The first cold pressure test: two unseen Easy and two unseen Medium in 45 minutes, no hints, timer visible — run as an experiment that produces data about your classifier.

    24 min read
  105. ·algorithms

    Mock Set 2 — Narrated & Recorded

    Two unseen Mediums solved entirely out loud, screen and audio recorded, then played back — the fastest available fix for design review communication.

    24 min read
  106. ·algorithms

    Blind 75 Sweep — Gap Audit

    Attempt-classify all 75 problems in one structured sweep, mark each cold, warm, hint or failed, and produce the personalised weak list that drives the rest of the track.

    25 min read
  107. ·algorithms

    Weak-Pattern Intensive

    Take the bottom three patterns from the L59 audit and repair them with the rebuild loop: blind template, three costumes, interleaved re-test.

    24 min read
  108. ·algorithms

    Mock Set 3 — One Hard, 45 min

    Decomposing an unfamiliar Hard: find the seam where it splits into two Mediums, and practise being productive for 45 minutes without a full solution.

    25 min read
  109. ·algorithms

    Company-Tagged — Microsoft & Amazon

    Work the frequency-ranked lists for the two companies that matter most to you, and adapt to each one's distinct review style rather than treating all loops as identical.

    21 min read
  110. ·algorithms

    Senior-Flavour Coding

    The hybrid round where coding meets design: rate limiters, LRU caches, schedulers and consistent hashing — built by composing primitives you already own.

    18 min read
  111. ·algorithms

    Contest Simulation

    A real timed LeetCode weekly contest — the closest available replica of timed-contest pressure, and the only place to practise performing rather than solving.

    24 min read
  112. ·algorithms

    Final Audit + Maintenance Plan

    Re-audit every pattern, compare against L59, and build the ongoing three-times-a-week loop that stops the whole thing decaying the moment the track ends.

    28 min read
  113. ·algorithms

    Algorithm practice · From recognition to a defensible solution

    A broad problem-family route alongside the runnable Foundations Lab: derive invariants, study variants, test with oracles and track specific gaps.

    22 min read
  114. ·machine learning

    Where LLMs Came From, and What They Actually Are

    A source-grounded history of language modelling, five core mechanisms and the boundaries between a predictor and a deployed assistant.

    22 min read
  115. ·machine learning

    Reading MEDEC — detection, localization and correction are different tests

    Audit the MEDEC benchmark's data construction, exact reported scores, prompt format and metric limitations without treating a clinical NLP benchmark as deployment validation.

    18 min read
  116. ·systems

    Diving deep into Tiktok recommendation engine

    Explain full-key embedding admission, expiry and incremental synchronization. Mechanisms, worked examples, failure analysis and complete practice answers.

    15 min read
  117. ·systems

    Kusto and KQL — pipelines, safe queries and honest windows

    Read KQL pipelines, reason about joins and aggregation, parameterize safe telemetry queries, and distinguish fixed bins from rolling windows.

    24 min read
  118. ·machine learning

    Reading OpenAI’s Math Repository: From Research Claims to Checkable Proofs

    A deep guide to OpenAI’s math release: proof versus tests, rational approximation, zeta zero-free regions, Lean, and what formal verification does—and does not—establish.

    30 min read
  119. ·systems

    RAG begins with an evidence boundary

    Build permission-filtered retrieval and a deterministic evidence packet before asking a model to synthesize an answer.

    24 min read
  120. ·systems

    Learning how to build an recommendation system from initial signals

    Build candidate and propensity-model evaluation contracts without future leakage. Mechanisms, worked examples, failure analysis and complete practice answers.

    20 min read
  121. ·systems

    Recommendation Systems From Scratch

    Candidate recall, exposure bias and constrained ranking. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    5 min read
  122. ·learning

    R01 · Week 1 Recall & Drill

    Week 1 revision: reproducible dev environments, Git's object model, shell pipelines, doc-hunting strategy, and Python's reference-based memory model.

    20 min read
  123. ·learning

    R02 · Week 2 Recall & Drill

    Week 2 revision: the iterator protocol behind for-loops, argument grammar and closures, data structure Big-O choices, class attribute lookup, and inheritance vs composition.

    20 min read
  124. ·learning

    R03 · Week 3 Recall & Drill

    Week 3 revision: exception discipline and pdb, import resolution and packaging, pytest fixtures and the TDD loop, type hints that no runtime enforces, and Big-O as a growth rate.

    20 min read
  125. ·learning

    R04 · Week 4 Recall & Drill

    Week 4 revision: discrete math as the language under SQL, vectors and cosine similarity, matrices as transformations, the chain rule, and gradient descent from scratch.

    20 min read
  126. ·learning

    R05 · Week 5 Recall & Drill

    Week 5 revision: distributions and Bayes' rule, what a p-value actually claims, two-pointer and sliding-window templates, hashmap internals, and linked-list surgeries.

    20 min read
  127. ·learning

    R06 · Week 6 Recall & Drill

    Week 6 revision: LIFO vs FIFO as a scheduling choice, recursion's three ingredients, tree traversal orders, heaps as partial order, and graph traversal with weights.

    20 min read
  128. ·learning

    R07 · Week 7 Recall & Drill

    Week 7 revision: sort trade-offs beyond Big-O, the two binary search templates, DP preconditions versus caching, greedy proofs and backtracking pruning, and normalisation to 3NF.

    20 min read
  129. ·learning

    R08 · Week 8 Recall & Drill

    Week 8 revision: SQL logical execution order, joins as filtered Cartesian products, aggregate NULL semantics, windows that preserve rows, and recursive CTEs.

    20 min read
  130. ·learning

    R09 · Week 9 Recall & Drill

    Week 9 revision: B-tree selectivity and composite index order, isolation levels and write skew, reading execution plans, the four NoSQL families, and star schema grain.

    20 min read
  131. ·learning

    R10 · Week 10 Recall & Drill

    Week 10 revision: bounded versus unbounded data, Spark stages and shuffles, Kafka as a log rather than a queue, watermarks and exactly-once effect, and idempotent orchestration.

    20 min read
  132. ·learning

    R11 · Week 11 Recall & Drill

    Week 11 revision: dbt as a compiler not an engine, lakehouse metadata layers over Parquet, the four data-quality pillars, lineage-driven governance and cost, and HTTP caching.

    20 min read
  133. ·learning

    R12 · Week 12 Recall & Drill

    Week 12 revision: resource modelling and idempotency keys, GraphQL's N+1 and cost limits, Protobuf field tags and RPC shapes, delegated authorisation versus identity, and Linux processes, memory, and file descriptors.

    20 min read
  134. ·learning

    R13 · Week 13 Recall & Drill

    Week 13 revision: TCP as a byte stream, L4 versus L7 load balancing, cache-aside and stampedes, CDN cache keys and Vary, and Docker layers as processes not VMs.

    20 min read
  135. ·learning

    R14 · Week 14 Recall & Drill

    Week 14 revision: declarative reconciliation over imperative starts, config and secrets injection, cloud identity and network isolation, Terraform state as authoritative mapping, and CAP versus PACELC.

    20 min read
  136. ·learning

    R15 · Week 15 Recall & Drill

    Week 15 revision: replication topologies and split-brain, consistency guarantees and their scope, Raft's real difficulty, hot partitions and consistent hashing, and at-least-once queues.

    20 min read
  137. ·learning

    R16 · Week 16 Recall & Drill

    Week 16 revision: RTO and RPO driving topology, which observability pillar answers which question, PromQL and cardinality, error budgets as budgets, and mitigate-before-diagnose.

    20 min read
  138. ·learning

    R17 · Week 17 Recall & Drill

    Week 17 revision: resource authorization, password KDFs, certificate trust and SAN checks, SQL injection boundaries, leakage-safe evaluation and least-squares gradients.

    40 min read
  139. ·learning

    R18 · Week 18 Recall & Drill

    Week 18 revision: likelihood and decision costs, ridge/lasso geometry, learning-curve assumptions, greedy tree impurity and measured ensemble diversity.

    40 min read
  140. ·learning

    R19 · Week 19 Recall & Drill

    Week 19 revision: negative-gradient boosting, tie-aware ranking metrics, leakage-free preprocessing, imbalance policies and honest evaluation of selected procedures.

    40 min read
  141. ·learning

    R20 · Week 20 Recall & Drill

    Week 20 revision: affine collapse and nonlinear XOR, batched MLP shapes, numerical backprop checks, optimizer recurrences and PyTorch mode/gradient contracts.

    40 min read
  142. ·learning

    R21 · Week 21 Recall & Drill

    Week 21 revision: dropout and normalization contracts, convolution shapes, recurrent Jacobian products, embedding objectives and controlled transfer-learning decisions.

    40 min read
  143. ·learning

    R22 · Week 22 Recall & Drill

    Week 22 revision: exact toy BPE, attention variance and tensor shapes, permutation equivariance, positional mechanisms and fixed-width versus KV-cache budgets.

    40 min read
  144. ·learning

    R23 · Week 23 Recall & Drill

    Week 23 revision: transformer block contracts, attention visibility, normalized decoding filters, conditional compute heuristics and exact streamed attention.

    40 min read
  145. ·learning

    R24 · Week 24 Recall & Drill

    Week 24 revision: prompting evaluation, chunk-span recovery, authorized hybrid ranking, exact-neighbor recall and bounded verified tool-workflow models.

    40 min read
  146. ·learning

    R25 · Week 25 Recall & Drill

    Worked revision of agent handoffs, judge bias, LoRA, KV-cache sizing, batching and multimodal extraction with bounded local code and source-backed answers.

    38 min read
  147. ·learning

    R26 · Week 26 Recall & Drill

    Worked system-design revision: explicit capacity assumptions, atomic identifier allocation, lost acknowledgements, feed work and enforced AI cost budgets.

    38 min read
  148. ·python

    Dev Environment — Linux/WSL, Terminal, VS Code

    The 90 minutes that saves you 90 hours. Real environment, real editor, real terminal — no ‘works on my machine’ for the next six months.

    22 min read
  149. ·python

    Git & GitHub — Commits, Branches, PRs

    The 90 minutes that turns Git from a scary black box into a save-point machine you trust with your career. Real commits, real branches, real PRs — the muscle memory every senior engineer runs on.

    26 min read
  150. ·python

    The Command Line — bash, pipes, grep, jq

    Live in the terminal without fear. The pipes, filters, and text-crunching muscle memory that separates an engineer from a button-clicker — and the 20 commands you'll use every single day for the rest of your career.

    24 min read
  151. ·python

    Reading Docs & Effective Googling — the Meta-Skill

    The single skill that separates a 10× engineer from a 1× engineer: knowing how to find the answer, fast, without asking a human. Man pages, official docs, GitHub source-diving, and search queries that actually work.

    24 min read
  152. ·python

    Python Variables & Types — Mental Model of Memory

    Not ‘what is a variable’ — the actual model of what happens in memory when you write `x = [1, 2, 3]`. References, mutability, boxes, arrows. The mental picture every senior Python dev has that every junior doesn't.

    22 min read
  153. ·python

    Control Flow — if/else, loops, comprehensions

    The three shapes of Python control flow every dev needs to reach for on reflex — branches, loops, comprehensions — with the rules for when each one is right and when it silently becomes unreadable.

    26 min read
  154. ·python

    Functions — arguments, scope, closures

    Functions are the atom of Python. This session covers the four kinds of arguments, the LEGB scope rule, closures, decorators as functions, and the classic tricks that trip up devs who thought they knew Python.

    24 min read
  155. ·python

    Data Structures — list, tuple, dict, set (when to use what)

    The one-page decision matrix that separates senior Python devs from the rest: given a data shape and a query pattern, know within 5 seconds which built-in structure to reach for — and its Big-O cost.

    25 min read
  156. ·python

    Classes & Objects — the OOP Mental Model

    Classes in Python are not what they are in Java. Everything is public, `self` is explicit, dunder methods are the interface. This session installs the mental model of what a class actually IS in Python — plus the three patterns you'll use daily.

    25 min read
  157. ·python

    Inheritance, Composition & Polymorphism

    The single most-abused feature in OOP is inheritance. This session teaches the ‘composition first’ rule every senior codebase uses, plus the MRO, super() rules, ABCs, protocols, and how Python's duck typing makes half of Java's ceremony unnecessary.

    26 min read
  158. ·python

    Errors, Exceptions & Debugging with pdb

    The mindset shift that turns ‘print statement warrior’ into ‘engineer who kills bugs in minutes’. Try/except done right, custom exceptions, tracebacks decoded, pdb keystrokes memorised, and the modern replacements (icecream, ipdb, structlog).

    27 min read
  159. ·python

    Modules, Packages, Virtualenvs, pip & uv

    How Python code is organised, versioned, and shipped — from a single script to an installable package, with reproducible envs on every machine.

    25 min read
  160. ·python

    Testing with pytest — TDD Workflow

    Turn code from hope into evidence: real pytest patterns — parametrize, fixtures, mocks, coverage — plus the TDD loop that makes refactoring safe.

    24 min read
  161. ·python

    Type Hints, mypy, dataclasses & pydantic

    Modern Python that scales past 1000 lines: gradual typing with mypy, immutable value objects with dataclasses, and runtime-validated boundaries with pydantic v2.

    25 min read
  162. ·python

    Big-O Notation — Reasoning About Scale

    How to talk about performance without measuring: growth rates, worst/avg/amortised cost, and the constant-factor traps that make theory disagree with reality.

    24 min read
  163. ·math

    Discrete Math — Sets, Logic, Combinatorics, Graphs

    The vocabulary of computer science: sets, boolean logic, counting arguments, and graph theory — the four discrete-math tools you'll use in every subsequent session.

    28 min read
  164. ·math

    Linear Algebra I — Vectors, Dot Product, Geometry

    The language ML speaks: vectors as arrows and lists of numbers, the dot product as similarity, norms as length, and cosine similarity as ‘how alike?’

    25 min read
  165. ·math

    Linear Algebra II — Matrices, Transforms, Eigenvalues

    Matrices as linear transformations, matrix multiplication as function composition, and eigenvalues as the axes a transform respects — the shape of every neural net.

    28 min read
  166. ·math

    Calculus I — Derivatives & Chain Rule

    Rate of change is the heart of learning: the derivative as slope, symbolic vs numeric differentiation, and the chain rule that powers every neural net.

    26 min read
  167. ·math

    Calculus II — Gradients & Gradient Descent from Scratch

    The one algorithm behind all of ML: gradients as the ‘uphill direction’ in n dimensions, SGD as the workhorse, and the learning-rate/momentum knobs that decide whether you converge or explode.

    27 min read
  168. ·math

    Probability — Random Variables, Distributions, Expectation

    Uncertainty, quantified: random variables, the distributions you'll actually meet (Bernoulli, binomial, normal, exponential, Poisson), expectation, variance, and Bayes' rule.

    27 min read
  169. ·math

    Statistics — CLT, Hypothesis Testing, Confidence Intervals

    The three ideas that let you turn noisy data into defensible claims: the Central Limit Theorem, p-values, and confidence intervals — with the mistakes that get careers cancelled.

    27 min read
  170. ·algorithms

    Arrays & Strings — Indexing, Slicing, Two-Pointer

    The two data structures every algorithm question secretly starts from — and the two-pointer template that solves half of them in O(n).

    26 min read
  171. ·algorithms

    Hashmaps & Sets — Hash Functions, Collisions

    The single data structure that turns O(n) loops into O(1) lookups — how it actually works under the hood, why it can go pathologically slow, and the design review patterns you must own.

    25 min read
  172. ·algorithms

    Linked Lists — Singly, Doubly, When They Win

    The data structure reviewers still love — plus the three real-world situations where a linked list actually beats an array.

    25 min read
  173. ·algorithms

    Stacks & Queues — LIFO/FIFO in Practice

    The two most important restricted data structures — and how they secretly power your function calls, browser history, printer queues, BFS, and every parser you've ever used.

    25 min read
  174. ·algorithms

    Recursion — Call Stack, Base Case, Worked Examples

    The mental model for solving problems by solving smaller versions of themselves — plus the tricks (memoisation, tail-form, iterative rewrites) that make it survive production.

    25 min read
  175. ·algorithms

    Trees & BSTs — Traversal (BFS/DFS)

    Trees are the recursive data structure that models everything hierarchical — DOM, filesystems, syntax, dependency graphs. Master traversal and balancing here, and every future algorithm gets easier.

    26 min read
  176. ·algorithms

    Heaps & Priority Queues

    The data structure behind top-K, Dijkstra, event schedulers, and every job runner — how heapq works, when to use it, and the classic patterns that come up in serious production work.

    26 min read
  177. ·algorithms

    Graphs — Representation, BFS, DFS, Shortest Path

    The most general data structure — and the algorithms that turn ‘find the shortest / cheapest / connected’ problems into 20-line functions.

    27 min read
  178. ·algorithms

    Sorting — Merge, Quick, and When to Trust the Built-in

    The three sorts everyone should know (merge, quick, heap), why Python's sorted() beats them all, and the practice problems that ask you to implement them anyway.

    27 min read
  179. ·algorithms

    Binary Search — the Pattern Behind 100 Problems

    Sorted (or monotonic) + halving = O(log n). One template, three shapes: classic search, lower/upper bound, and binary-search-on-the-answer. The pattern behind git bisect, B-tree lookups, ship-in-D-days, and half the LeetCode medium set.

    27 min read
  180. ·algorithms

    Dynamic Programming — Memoisation & Tabulation

    Break the problem down, cache the answer. Overlapping subproblems + optimal substructure = polynomial time from exponential recursion. Two dialects (top-down memo, bottom-up tabulation), one recipe (state → transition → base case → order), and the classic classics: Fibonacci, climbing stairs, coin change, LIS, edit distance.

    28 min read
  181. ·algorithms

    Greedy & Backtracking — When to Use Each

    Two decision-making patterns that live either side of DP. Greedy: bet on the best local move and never look back — fast, occasionally wrong. Backtracking: explore every option and undo dead ends — slow, always right. Learn to prove greedy is safe, prune backtracking aggressively, and pick the right tool in 30 seconds.

    27 min read
  182. ·data engineering

    The Relational Model — Tables, Keys, Normalisation

    Design keys, dependencies and historical facts; normalise worked schemas and test real SQLite constraints.

    18 min read
  183. ·data engineering

    SQL Basics — SELECT, WHERE, ORDER BY, LIMIT

    Query rows safely with explicit NULL, alias, ordering and pagination semantics, verified against exact SQLite results.

    16 min read
  184. ·data engineering

    Joins — INNER, LEFT, RIGHT, FULL, Anti-Join

    Choose join semantics, preserve measure grain and compare physical algorithms without fan-out or NULL mistakes.

    17 min read
  185. ·data engineering

    Aggregations — GROUP BY, HAVING, Subqueries

    Compute honest grouped metrics, exact medians and weighted rollups; distinguish missing populations and approximation contracts.

    16 min read
  186. ·data engineering

    Window Functions — the Game-Changer

    Rank deterministically, reason about peers and frames, and compute calendar-aware deltas and session boundaries.

    17 min read
  187. ·data engineering

    CTEs & Recursive Queries

    Compose named SQL stages and safely traverse graphs with explicit cycle, reachability and truncation semantics.

    17 min read
  188. ·data engineering

    Indexes — B-Tree Intuition, When to Add

    Design and validate query-driven indexes; distinguish access paths, output work, visibility and concurrent-build safety.

    16 min read
  189. ·data engineering

    Transactions & ACID — Isolation Levels, MVCC

    Protect transaction invariants with precise isolation, retry and durability contracts; test local rollback and bounded anomaly models.

    18 min read
  190. ·data engineering

    Query Planning — EXPLAIN, Execution Plans, Tuning

    A query returning ten rows can still scan millions, build a large hash table, or repeat a cheap lookup thousands of times. An index is one possible remedy, not a diagnosis. The objective is to read PostgreSQL 16 plans, distinguish

    20 min read
  191. ·data engineering

    NoSQL Landscape — KV, Document, Column, Graph

    “NoSQL” is an umbrella, not a transaction or performance contract. Key-value, document, wide-column and graph describe different ways to organize access; products often span families. The goal is to explain all four, model Cassand

    20 min read
  192. ·data engineering

    Data Modelling — Dimensional, Data Vault, OBT

    A warehouse needs an agreed meaning for one row before it needs a fashionable schema. This lesson designs a sales star, distinguishes Kimball, Inmon, Data Vault and one-big-table (OBT) approaches, implements historical customer at

    20 min read
  193. ·data engineering

    Batch vs Streaming — Mental Model & Use Cases

    “Real time” is a requirement to quantify, not an engine to buy. The goal is to classify workloads by input boundedness, freshness and repair semantics, then justify batch, micro-batch or record-at-a-time processing with explicit a

    20 min read
  194. ·data engineering

    Spark — RDD, DataFrame, Jobs/Stages/Shuffles

    Spark tuning begins with an execution model, not “add executors.” This lesson traces DataFrame expressions through logical/physical plans, jobs, stages, tasks and exchanges, then reasons about skew, broadcast, caching and small fi

    20 min read
  195. ·data engineering

    Kafka — Topics, Partitions, Consumer Groups

    Kafka is a partitioned retained log with independent readers. Treating offset commits as deletion, replication as invulnerability, or a transaction flag as protection for every downstream effect causes design errors. This lesson t

    20 min read
  196. ·data engineering

    Stream Processing — Watermarks, Windows, Exactly-Once

    A loop reading Kafka is not yet a correct stateful processor. This lesson defines time, window membership, progress, emission, state cleanup and sink effects separately. It targets **Spark 3.5.7** and **Flink 1.18** where their co

    20 min read
  197. ·data engineering

    Orchestration — Airflow, DAGs, Retries, Backfills

    Orchestration coordinates dependencies, scheduling, retries and historical runs. It does not make arbitrary writes atomic or correct. This lesson targets **Airflow 2.10.5** and preserves the full daily-order pipeline, sensor, retr

    20 min read
  198. ·data engineering

    dbt — Models, Tests, Docs, Warehouse-Native ELT

    Structure staging, intermediate and mart models with explicit grain; Use ref, source, macros and generic/singular test contracts; Choose materialisations and reconcile late changes, updates and deletes.

    20 min read
  199. ·data engineering

    Lakehouse — Delta / Iceberg / Hudi, ACID on Files

    Explain atomic snapshot membership and validated commit retries; Trace Delta versions and distinguish compaction from retention; Compare Delta, Iceberg and Hudi compatibility and maintenance.

    20 min read
  200. ·data engineering

    Data Quality — Freshness, Volume, Schema, Distribution

    Check eligible freshness, volume, schema, validity and distribution; Distinguish unknown checks from passing data and route by consequence; Design consumer-specific publication gates and seasonal baselines.

    20 min read
  201. ·data engineering

    Governance & Cost — Lineage, PII, Attribution

    Trace column dependencies and enforce classification separately; Reconcile direct, shared and unallocated cost against a declared total; Design justified retention and verifiable authorised erasure workflows.

    20 min read
  202. ·systems

    HTTP Fundamentals — Verbs, Status Codes, Headers, Caching

    Interpret HTTP messages, methods and conditional response semantics; Separate cache freshness, validation, Vary and private data policies; Explain protocol versions, session state and bounded retry contracts.

    20 min read
  203. ·systems

    REST API Design — Resources, Versioning, Idempotency

    Design resources, domain actions, errors and compatible evolution; Implement atomic operation replay and bounded total-order pagination; Describe OpenAPI, correct deprecation dates and patch semantics.

    20 min read
  204. ·systems

    GraphQL — Schema, Resolvers, N+1, When to Pick It

    Trace typed GraphQL execution, nullability and mutation ordering; Compare exact naive and batched lookup results with scoped authorisation; Bound queries and distinguish persisted documents from allowlists.

    20 min read
  205. ·systems

    gRPC & Protobuf — When RPC Wins

    Define RPC messages and four streaming shapes with explicit limits; Verify Protobuf bytes, presence and mixed-schema compatibility; Distinguish message framing, deadlines, cancellation and durable effects.

    20 min read
  206. ·systems

    AuthN & AuthZ — OAuth 2.0, OIDC, JWT

    Token validation is more than decoding. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    20 min read
  207. ·systems

    OS Basics — Processes, Threads, Memory, FDs

    Processes, threads and resource accounting. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    18 min read
  208. ·systems

    Networking I — TCP/IP, DNS, Sockets

    A reliable byte stream is not a durable message protocol. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    18 min read
  209. ·systems

    Networking II — Load Balancers L4 vs L7, Reverse Proxies

    Balance work, drain connections and bound retries. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    17 min read
  210. ·systems

    Caching — Cache-Aside, Write-Through, TTLs, Invalidation

    Cache-aside races and lease ownership. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    18 min read
  211. ·systems

    CDN — Edge, Cache Hierarchies, Cache-Control

    Cache keys are isolation boundaries. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    20 min read
  212. ·cloud engineering

    Docker — Images, Layers, Dockerfile, Networking

    Understand container images, cache invalidation, runtime isolation and service networking through a multi-stage Python reference design and measured acceptance criteria.

    29 min read
  213. ·cloud engineering

    Kubernetes I — Pods, Deployments, Services

    Kubernetes without the mysticism — Pods run containers, Deployments keep N of them alive, Services give them a stable IP. Reason through and optionally deploy a local app, with selectors, probes and rollout failure analysis.

    23 min read
  214. ·cloud engineering

    Kubernetes II — ConfigMaps, Secrets, HPA, Network Policies

    Connect configuration, secret rotation, autoscaling and network isolation to a complete reference workload, then reason through controller and recovery failures.

    38 min read
  215. ·cloud engineering

    Azure Cloud — Identity, Storage, Networking, App Service

    The four pillars of every real Azure workload — Entra ID + RBAC, Storage & Cosmos, VNets & Private Endpoints, App Service & Container Apps. What to pick and why.

    28 min read
  216. ·cloud engineering

    Infrastructure as Code — Terraform / Bicep Basics

    Build a versioned Azure Terraform module on paper, understand state and dependency graphs, and rehearse plan review, drift, import, refactoring and recovery without cloud writes.

    37 min read
  217. ·systems

    CAP & PACELC — the Actual Trade-Offs

    Reason from operation histories to CAP and PACELC, compare configured database contracts, and choose consistency for checkout.

    20 min read
  218. ·systems

    Replication — Leader/Follower, Multi-Leader, Leaderless

    Compare replication topologies, acknowledgment boundaries and lag; reason about quorum limits, session positions and fenced failover.

    19 min read
  219. ·systems

    Consistency Models — Linearizable, Sequential, Eventual

    Test consistency with precise operation histories, independent session guarantees and bounded Python checks; choose contracts by invariant.

    20 min read
  220. ·systems

    Consensus — Paxos & Raft Intuition

    Quorum intersection is necessary but protocol rules carry the value. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    18 min read
  221. ·systems

    Sharding & Partitioning Strategies

    Choose hash, range or directory routing, measure movement and hot keys, and plan a versioned snapshot/stream migration with safe cutover.

    19 min read
  222. ·systems

    Message Queues — SQS, RabbitMQ, Kafka as Queue

    Separate delivery attempts from business effects; compare queue/log contracts, budget retries and build a bounded idempotent-consumer model.

    19 min read
  223. ·systems

    Multi-Region — Active-Passive, Active-Active, Failover

    Match regional data authority, spare capacity and DNS recovery to RTO/RPO objectives; work through loss, fencing and failback examples.

    18 min read
  224. ·systems

    The 3 Pillars — Metrics, Logs, Traces

    Signals answer questions only if context survives. A source-bounded lesson with worked reasoning, failure analysis and explicit runtime limitations.

    20 min read
  225. ·systems

    Prometheus, Grafana, OpenTelemetry — Hands-on

    Follow telemetry from instrumentation to queries and decisions: versioned stack wiring, weighted ratios, histogram semantics, dashboards and alert failure modes.

    20 min read
  226. ·systems

    SLIs, SLOs & Error Budgets — the SRE Math

    Define reliability in the right units, derive error budgets and burn rates, and test rolling-window alerts without confusing requests with downtime.

    20 min read
  227. ·systems

    Incident Response — Runbooks, Postmortems, On-Call

    Coordinate technical response and communications, choose safe mitigations, verify full recovery and turn evidence into accountable learning.

    20 min read
  228. ·systems

    AuthN vs AuthZ, Sessions & Password Storage

    Separate credential validation from permission decisions; reason about password storage, sessions, JWTs, revocation, tenant isolation and safe local tests.

    20 min read
  229. ·systems

    TLS 1.3, PKI & Cert Lifecycle

    Trace TLS 1.3 authentication and key agreement, inspect PKI trust boundaries, and operate certificate lifecycles without disabling verification.

    21 min read
  230. ·systems

    OWASP Top 10, Secrets Mgmt & Threat Modelling

    Use the OWASP Top 10:2021 as a bounded risk map, then test interpreter and access boundaries and design secrets, STRIDE and dependency controls.

    21 min read
  231. ·machine learning

    The ML Mental Model — Features, Labels, Train/Val/Test

    Design an honest supervised-learning experiment, diagnose five leakage mechanisms, compare losses and metrics, and test a small regression pipeline without downloads.

    24 min read
  232. ·machine learning

    Linear Regression from Scratch: Solvers, Geometry and Evidence

    Derive least squares, test gradients and projection geometry, recover its history, and compare stable and iterative solvers.

    20 min read
  233. ·machine learning

    Logistic Regression — Sigmoid, Cross-Entropy, from Scratch

    Derive linear log-odds, stable binary cross-entropy and its gradient; separate calibration, ranking and validation-selected decisions.

    15 min read
  234. ·machine learning

    Regularization — L1, L2, Elastic Net

    Derive ridge, lasso and elastic net; verify normalization, soft thresholding, fold-safe tuning and the AdamW distinction.

    15 min read
  235. ·machine learning

    Bias–Variance Trade-off & Learning Curves

    Derive squared-error bias, variance and noise; measure independent refits and bootstrap limits, and interpret learning curves carefully.

    16 min read
  236. ·machine learning

    Decision Trees — Gini, Entropy, Splits

    Calculate weighted impurity gains, implement a greedy tree, trace predictions and diagnose leaf-size, pruning and representation limits.

    16 min read
  237. ·machine learning

    Random Forest & Bagging

    Build a per-split randomized forest, derive bootstrap coverage and covariance limits, and audit out-of-bag evaluation and feature importance.

    16 min read
  238. ·machine learning

    Gradient Boosting — XGBoost, LightGBM

    Derive gradient and regularized Newton tree updates; run bounded XGBoost and LightGBM experiments with validation-controlled stages.

    16 min read
  239. ·machine learning

    Evaluation Metrics — P/R/F1/ROC/PR/AUC

    Derive confusion-matrix, ROC and average-precision metrics; select thresholds without test leakage and account for prevalence and capacity.

    16 min read
  240. ·machine learning

    Feature Engineering — Encoding, Scaling, Missing

    Build a fold-safe heterogeneous feature pipeline; test encoding, missingness, learned state, target cross-fitting and persistence boundaries.

    19 min read
  241. ·machine learning

    Imbalanced Data — SMOTE, Class Weights, Thresholds

    Separate ranking, calibration and threshold decisions under imbalance. Apply weighted learning and fold-local resampling without leakage.

    15 min read
  242. ·machine learning

    Model Selection — CV, Hyperparameter Tuning, Optuna

    Choose split units and time boundaries that match deployment. Distinguish nested evaluation from hyperparameter selection.

    15 min read
  243. ·machine learning

    Perceptron & Activation Functions

    Derive perceptron updates and the XOR impossibility proof. Compare activation derivatives and failure modes.

    15 min read
  244. ·machine learning

    Multi-Layer Perceptron — Forward Pass

    Trace forward-pass shapes and count every parameter. Explain initialization and approximation assumptions.

    15 min read
  245. ·machine learning

    Backpropagation — Derived by Hand on a 2-Layer Net

    Derive affine and activation gradients including biases. Check complete NumPy gradients against numerical and autograd references.

    15 min read
  246. ·machine learning

    Optimizers — SGD, Momentum, Adam, RMSprop

    Implement and compare SGD, momentum, RMSprop and Adam updates. Derive startup correction and decoupled weight decay.

    15 min read
  247. ·machine learning

    PyTorch Fundamentals — Tensors, Autograd, nn.Module

    Use tensor storage, dtype, device and gradient contracts. Build registered modules and a validation-safe training loop.

    15 min read
  248. ·machine learning

    Regularization in DL — Dropout, BatchNorm, Weight Decay

    Derive dropout moments and distinguish normalization axes. Explain coupled versus decoupled decay and train-eval state.

    15 min read
  249. ·machine learning

    CNNs — Convolution, Pooling, ImageNet Architectures

    CNNs — Convolution, Pooling, ImageNet Architectures: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    45 min read
  250. ·machine learning

    RNNs & LSTMs — Sequences & the Vanishing Gradient

    RNNs & LSTMs — Sequences & the Vanishing Gradient: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    45 min read
  251. ·machine learning

    Embeddings — word2vec, GloVe, Contrastive Learning

    Embeddings — word2vec, GloVe, Contrastive Learning: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    45 min read
  252. ·machine learning

    Transfer Learning & Fine-Tuning Classical DL

    Transfer Learning & Fine-Tuning Classical DL: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    45 min read
  253. ·machine learning

    Tokenization — BPE, WordPiece, SentencePiece

    Tokenization — BPE, WordPiece, SentencePiece: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    45 min read
  254. ·machine learning

    Attention Intuition — Sequence Bottlenecks and Soft Retrieval

    Attention Intuition — Sequence Bottlenecks and Soft Retrieval: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    45 min read
  255. ·machine learning

    Q/K/V Math — Scaled Dot-Product Attention Derived

    Q/K/V Math — Scaled Dot-Product Attention Derived: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    45 min read
  256. ·machine learning

    Multi-Head Attention — Parallel Views

    Multi-Head Attention — Parallel Views: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    45 min read
  257. ·machine learning

    Positional Encoding — Sinusoidal, Learned, RoPE

    Prove attention equivariance, derive sinusoidal and rotary position geometry, and test offsets without confusing computable positions with length generalization.

    20 min read
  258. ·machine learning

    Full Transformer Architecture — Encoder + Decoder

    Assemble causal and encoder-decoder Transformers, derive residual and normalization behavior, count parameters, and train a tiny CPU character fixture.

    20 min read
  259. ·machine learning

    Encoder (BERT), Decoder (GPT), Enc-Dec (T5) — When Each

    Separate Transformer families, pretraining losses and output heads; work through BERT corruption and T5 sentinels and inspect local-only inference interfaces.

    20 min read
  260. ·machine learning

    LLM Sampling — Greedy, Beam, Top-k, Top-p, Temperature

    Derive temperature, nucleus truncation and search; implement edge-case-safe CPU sampling and translate policies into versioned API contracts.

    20 min read
  261. ·machine learning

    Scaling Laws — Chinchilla, Compute-Optimal Training

    Derive budget-conserving language-model allocations, reconcile Chinchilla and Kaplan, and compare training-only and lifetime-cost objectives.

    20 min read
  262. ·machine learning

    Efficient Attention — Flash, Sparse, Linear

    Derive online softmax, distinguish exact execution from sparse and kernel operators, and verify CPU parity while specifying a separate GPU-backend proof.

    20 min read
  263. ·machine learning

    Prompting — Zero-Shot, Few-Shot, Chain-of-Thought, ReAct

    Design testable prompts, bounded tool controllers and evaluation contracts; distinguish published reasoning results from offline fixtures and generated explanations.

    20 min read
  264. ·machine learning

    RAG I — Chunking Strategies & Indexing

    Build a versioned RAG index with source ranges, tokenizer budgets, stale-chunk removal and access controls; test a complete local lexical-index lifecycle.

    20 min read
  265. ·machine learning

    RAG II — Retrieval, Hybrid Search, Reranking

    RAG II — Retrieval, Hybrid Search, Reranking: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    18 min read
  266. ·machine learning

    Vector Databases — pgvector, HNSW, IVF

    Vector Databases — pgvector, HNSW, IVF: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    18 min read
  267. ·machine learning

    LLM Agents — Function Calling, Tools, Planning

    LLM Agents — Function Calling, Tools, Planning: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    18 min read
  268. ·machine learning

    Multi-Agent Orchestration — LangGraph, CrewAI Patterns

    Multi-Agent Orchestration — LangGraph, CrewAI Patterns: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    18 min read
  269. ·machine learning

    LLM Evaluation — LLM-as-Judge, RAGAS, Golden Sets

    LLM Evaluation — LLM-as-Judge, RAGAS, Golden Sets: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    18 min read
  270. ·machine learning

    Fine-Tuning — LoRA, QLoRA, PEFT, When NOT to Fine-Tune

    Fine-Tuning — LoRA, QLoRA, PEFT, When NOT to Fine-Tune: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    18 min read
  271. ·machine learning

    LLM Serving — KV Cache, Batching, Speculative Decoding

    LLM Serving — KV Cache, Batching, Speculative Decoding: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    18 min read
  272. ·machine learning

    Multimodal LLMs — CLIP, VLMs, Audio, Video

    Multimodal LLMs — CLIP, VLMs, Audio, Video: mechanisms, worked examples, assumptions and source-backed corrections with explicit experiment boundaries.

    18 min read
  273. ·systems

    System Design Framework — Reqs, Capacity, HLD, Deep-Dive

    A worked design-review method grounded in measurable requirements, consistent capacity arithmetic, complete request paths and defensible failure tradeoffs.

    21 min read
  274. ·systems

    Design a URL Shortener — the Classic Warm-Up

    Design a shortener around authoritative mappings, unique allocation, explicit redirect caching and takedown policies, with executable failure models.

    23 min read
  275. ·systems

    Design a Chat System — WebSockets, Delivery, Presence

    Design idempotent durable chat acceptance, ordering, replay and receipts. Mechanisms, worked examples, failure analysis and complete practice answers.

    18 min read
  276. ·systems

    Design a Newsfeed / Recommender — Pull vs Push, Ranking

    Derive push and pull costs from follower and reader activity. Mechanisms, worked examples, failure analysis and complete practice answers.

    17 min read
  277. ·systems

    Design an AI Chat Product — RAG + Agents + Serving

    Design durable turn state, authorized retrieval and tool execution. Mechanisms, worked examples, failure analysis and complete practice answers.

    19 min read
  278. ·machine learning

    Arrays, shapes, and the first linear model

    Master array ownership and axes, then audit attention, context and quantization claims with exact CPU checks.

    33 min read
  279. ·machine learning

    Vectors, Matrices, and the Geometry of Data

    Derive geometry, matrix products, SVD and retrieval scores while testing the limits of each analogy.

    18 min read
  280. ·machine learning

    Broadcasting — The Rule That Runs the World

    Predict shape sharing, memory costs and numerical failure cases in NumPy and transformer patterns.

    15 min read
  281. ·machine learning

    Derivatives are local measurements; backprop is bookkeeping

    Rebuild the chain rule from local sensitivities through scalar autograd, matrix pullbacks and checkpointing.

    19 min read
  282. ·machine learning

    Probability, cross-entropy, and stable logits

    Derive information measures and stable probability losses, then distinguish modern language and preference objectives.

    18 min read
  283. ·machine learning

    Optimization: steps, momentum, AdamW, and honest experiments

    Trace optimizer updates and numerical safeguards without mistaking toy convergence for universal model performance.

    17 min read
  284. ·machine learning

    One neuron: logistic regression, stable loss, and its boundary

    Train and audit a sigmoid neuron, verify exact framework parity, and prove and repair its XOR limitation.

    17 min read
  285. ·machine learning

    Activation Functions — sigmoid, tanh, ReLU, GELU, SwiGLU, xIELU

    Derive and test activation functions, full gradient chains, gated parameter budgets and source-corrected xIELU.

    17 min read
  286. ·machine learning

    The Forward Pass: Shapes, XOR and Parameter Counts

    Compute an MLP by hand, construct a strict-margin XOR classifier, and distinguish actual architecture counts from universal claims.

    20 min read
  287. ·machine learning

    Backprop by Hand: Nine Gradients and a Verified XOR Network

    Derive all nine ReLU-network gradients, preserve the tanh XOR experiment, and verify finite differences against CPU PyTorch.

    20 min read
  288. ·machine learning

    MLP on MNIST: A Complete Local-Only NumPy Recipe

    Load existing local IDX files, implement stable multiclass loss and backpropagation, and separate a synthetic contract from real digit evaluation.

    20 min read
  289. ·machine learning

    Micrograd: Build and Test a Scalar Autograd Engine

    Implement complete scalar reverse-mode differentiation, shared-edge accumulation, stable cross entropy and a four-point neural network.

    20 min read
  290. ·machine learning

    Vectorization: Measure Speed, Shapes and Memory

    Compare exact scalar and array programs, derive einsum contractions and FLOP counts, and measure performance without promised speedup factors.

    20 min read
  291. ·machine learning

    PyTorch Tensors and Autograd: Leaves, VJPs and Safe Updates

    Port NumPy mathematics to raw PyTorch tensors and verify gradient accumulation, cotangents, graph lifetime and mutation controls.

    20 min read
  292. ·machine learning

    nn.Module: Registration, Composition and Checkpoint Contracts

    Structure models with registered parameters and buffers, distinguish eval from no-grad, and verify trusted state/config round-trips.

    20 min read
  293. ·machine learning

    Datasets, DataLoaders and Collate: Coverage Before Throughput

    Test indexed sampling, ragged collation, worker/rank sharding and local stream resume while treating optional cloud adapters as unexecuted.

    20 min read
  294. ·machine learning

    The Training Loop, Logging, and Reproducibility

    Build and verify a resumable training state machine with RNG, sampler, optimizer, scheduler, EMA and safe checkpoints.

    16 min read
  295. ·machine learning

    GPU and Mixed Precision

    Separate device placement, operation-specific mixed precision, loss scaling and measured performance without numerical myths.

    15 min read
  296. ·machine learning

    Debugging — nan, inf, and Overfitting a Single Batch

    Diagnose training with exact objective contracts, finite checks, tiny-batch fits, negative controls and profiling.

    15 min read
  297. ·machine learning

    Dropout and generalization — masks, scaling and controlled experiments

    Derive dropout moments, preserve leakage-resistant evaluation, test mask variants and choose regularization by controlled experiments.

    19 min read
  298. ·machine learning

    Batch Norm, Layer Norm, and RMSNorm — the normalization tour

    Derive normalization axes, affine and buffer contracts, implement BN/LN/RMSNorm and test train/eval and calibration failures.

    16 min read
  299. ·machine learning

    Weight Initialization — Xavier, He, and μP

    Derive fan and second-moment initialization, test activation and gradient propagation, and understand bounded width-transfer parameterizations.

    15 min read
  300. ·machine learning

    Schedulers — Warmup, Cosine, One-Cycle, and WSD

    Implement and verify warmup, linear, cosine, one-cycle and WSD clocks, resume behavior and fair schedule comparisons.

    17 min read
  301. ·machine learning

    Gradient Clipping and Accumulation

    Derive weighted accumulation and global clipping, flush unequal tails and distinguish AMP, DDP and activation-checkpointing contracts.

    17 min read
  302. ·machine learning

    Convolution: local shared operators, shapes and gradients

    Compute original convolution examples and general output shapes Implement multi-channel forward and backward accumulation Compare receptive fields, pooling and modern convolution designs.

    20 min read
  303. ·machine learning

    CNN architectures: LeNet, AlexNet, residual learning and modern backbones

    Build LeNet-like and ResNet18 models with exact parameter counts Distinguish degradation from vanishing gradients Design fair architecture and local-data comparisons.

    20 min read
  304. ·machine learning

    CIFAR-10 training: a complete local pipeline and controlled experiments

    Build a complete local CIFAR training and selection pipeline Test normalization, parameter groups and weighted evaluation Diagnose training failures with controlled ablations.

    20 min read
  305. ·machine learning

    Transfer learning: frozen features, fine-tuning and buffer discipline

    Implement local-checkpoint linear and fine-tuning regimes Freeze parameters and BatchNorm buffers deliberately Compare transfer objectives and source-target assumptions.

    20 min read
  306. ·machine learning

    Data augmentation: tested mixing, task assumptions and calibration

    Implement mixup and clipped-area CutMix with exact targets Compute calibration and soft-target loss controls Choose task-valid augmentation and controlled ablations.

    20 min read
  307. ·machine learning

    Vision Transformers: patch equivalence, position and attention cost

    Prove patch projection output and gradient equivalence Build and test a small complete Vision Transformer Explain position interpolation, parameter counts and quadratic cost.

    20 min read
  308. ·machine learning

    Word2Vec: complete skip-gram training, geometry and honest evaluation

    Train complete skip-gram negative sampling on bundled text Derive lookup and binary-loss gradients and sampling contracts Query and evaluate embedding geometry without semantic guarantees.

    20 min read
  309. ·machine learning

    RNNs from scratch: complete BPTT, character generation and structured recurrence

    Implement complete NumPy BPTT and verify every coordinate Train and generate with a complete character RNN locally Distinguish clipping, truncation, gates, attention and affine scans.

    20 min read
  310. ·machine learning

    LSTM and GRU — Gates, State and Gradient Paths

    An ordinary RNN repeatedly applies a nonlinear state transformation. Its time derivative is a product of **time-varying Jacobians**, not just the recurrent matrix's eigenvalue raised to a power. LSTM introduced a separately carried cell state; the la

    20 min read
  311. ·machine learning

    Seq2Seq — A Complete Length-Aware Encoder–Decoder

    A sequence-to-sequence model defines a conditional distribution over a target sequence given a source. In the fixed-state recurrent version, an encoder reads the source and passes its final state to an autoregressive decoder. For an LSTM the interfac

    20 min read
  312. ·machine learning

    Why Attention — Query-Dependent Source Access

    A fixed-state encoder-decoder must route all source information through its terminal state. Attention retains the sequence of encoder representations and lets each decoder step retrieve a different weighted context. This removes the requirement that

    20 min read
  313. ·machine learning

    Attention is a weighted sum with a precise mask

    Calculate attention numerically, derive its softmax backward pass, and test causal and permutation properties.

    24 min read
  314. ·machine learning

    Multi-Head Attention — Shapes, Specialization and KV Budgets

    A single attention head already forms a distribution over many keys; it is not forced to pick exactly one token. Multi-head attention gives several independently parameterized distributions and value projections, then mixes their results. At fixed mo

    20 min read
  315. ·machine learning

    Positional Encodings — Sinusoids, Learned Tables and RoPE

    Unmasked self-attention with shared tokenwise projections and no position signal is **permutation-equivariant**: permuting input rows permutes output rows. It is not invariant unless an additional permutation-invariant readout removes row order. Thus

    20 min read
  316. ·machine learning

    Transformer Blocks — Full Architectures and an Analytic Decoder

    Attention mixes information across token positions. A position-wise feed-forward network transforms features with the **same weights at each position**. Normalization sets a branch's input or output scale, and residual addition carries an explicit sk

    20 min read
  317. ·machine learning

    nanoGPT Rebuilt — A Complete Tested Decoder

    The useful exercise in nanoGPT is tracing a compact decoder-only model end to end: configuration, embeddings, fused QKV attention, pre-norm blocks, final norm, tied output projection, optimizer groups and generation. Its public model/train files are

    20 min read
  318. ·machine learning

    Training a Decoder on Local Text — Tiny Shakespeare Recipe

    A small character-level decoder is a useful way to inspect tokenization, shifted targets, causal loss, optimizer state and generation. Tiny Shakespeare is one possible **already-local** corpus, not data bundled or downloaded by this audit. This lesso

    20 min read
  319. ·machine learning

    KV caching: correct positions, masks, memory and reuse

    Implement and test a complete cached decoder, derive cache memory, and distinguish paging, sharing, compression and eviction.

    18 min read
  320. ·machine learning

    RoPE and FlashAttention: relative positions and online softmax

    Derive rotary attention and tiled normalization, test CPU parity, and separate positional extension from GPU kernel performance.

    18 min read
  321. ·machine learning

    Byte-pair encoding: merges, Unicode and artifact contracts

    Build and inspect deterministic byte BPE, correct weighted merge traces, preserve Unicode bytes and freeze tokenizer artifacts.

    18 min read
  322. ·machine learning

    SentencePiece and unigram: lattices, normalization and compatibility

    Derive unigram marginal likelihood and soft EM, test segmentation, and distinguish tokenizer algorithms from toolkit and normalization choices.

    17 min read
  323. ·machine learning

    Pretraining data: auditable extraction, grouping and token shards

    Design a provenance-aware pretraining pipeline with tested filters, grouped splits, boundary-safe windows and validated token shards.

    20 min read
  324. ·machine learning

    Chinchilla scaling: fit assumptions, budgets and serving cost

    Derive compute-constrained allocation, correct the numerical budget, and separate fixed-ratio heuristics from fitted and inference-aware scaling.

    15 min read
  325. ·machine learning

    Data mixing: sampling, exposure, proxy ablations and curriculum

    Implement weighted shard sampling, measure domain exposure, run a complete synthetic ablation and explain DoReMi and token-clock schedules.

    16 min read
  326. ·machine learning

    Quality and deduplication: MinHash, LSH and measured decisions

    Implement probabilistic near-duplicate retrieval with exact verification, audit learned quality policies and screen contamination with explicit limits.

    19 min read
  327. ·machine learning

    Architecture choices: derive and test a 100M decoder

    Implement pre-norm, RMSNorm, RoPE, GQA and SwiGLU; reconcile exact model counts, cache budgets and modern architecture claims.

    18 min read
  328. ·machine learning

    Distributed Training Basics — DDP and FSDP

    Derive distributed-training memory and communication costs, implement rank-aware reference loops, and distinguish DDP, ZeRO and FSDP2.

    17 min read
  329. ·machine learning

    Renting Your First GPU — Runpod / Modal / Vast.ai Walkthrough

    Choose GPU resources from measured workloads, compare service lifecycles, and plan safe transfer, monitoring, checkpointing and teardown.

    17 min read
  330. ·machine learning

    Training a 100M model: complete local recipe and budget

    Build a local-shard training state machine with exact token budgets, validation, persistence and honest resource-dependent execution limits.

    14 min read
  331. ·machine learning

    Loss curves and evaluation: likelihood, tasks and controls

    Preserve the exact synthetic decoder experiment while restoring token-weighted metrics, downstream evaluation, uncertainty and contamination audits.

    18 min read
  332. ·machine learning

    Checkpointing and resuming: consistent state and durable publication

    Implement trusted local restart snapshots, test continuation and failures, and derive retention and distributed recovery boundaries.

    15 min read
  333. ·machine learning

    Pretraining bugs: hypotheses, counterexamples and tests

    Diagnose stalled, nonfinite, drifting or misleading training runs through bounded interventions rather than loss-curve folklore.

    14 min read
  334. ·machine learning

    Scaling from 100M to 1B — A Mental Model

    Calculate compute, memory and elapsed-time ranges across model scales, interpret published receipts, and plan infrastructure from measured constraints.

    15 min read
  335. ·machine learning

    Supervised fine-tuning: objective, templates and local recipes

    Derive assistant-only supervision, test masks and conditioning gradients, and specify pinned local SFT with template and regression checks.

    16 min read
  336. ·machine learning

    Instruction datasets: provenance, normalization and mixtures

    Audit exact dataset identities and rights, reconstruct conversation trees, and derive reproducible example and supervised-token sampling weights.

    18 min read
  337. ·machine learning

    Adaptation with LoRA: low-rank updates and masked supervision

    Derive low-rank adapter gradients, inject and test a complete layer, and audit versioned SFT, merge and variant workflows.

    16 min read
  338. ·machine learning

    QLoRA: NF4 storage, gradients and local integration

    Derive block-scale memory, implement a CPU NF4 teaching quantizer, and distinguish adapter gradients, paging and merge behavior.

    15 min read
  339. ·machine learning

    Reward Modeling: Pairwise Likelihood, Data and Failure Modes

    Derive preference likelihoods, test reward gradients and pooling, and audit data, calibration and reward hacking.

    20 min read
  340. ·machine learning

    RLHF with PPO — Intuition + Minimal Code

    Derive PPO clipping and GAE, execute a complete tiny CPU loop, and audit language-model trainer, reward and modern RL workflows.

    17 min read
  341. ·machine learning

    DPO — RLHF without the RL

    Derive DPO from KL-regularized rewards, test masked log probabilities and gradients, and compare preference objectives and trainer contracts.

    16 min read
  342. ·machine learning

    Evaluation and Red-Teaming: Protocols, Uncertainty and Safety

    Build reproducible capability, chat, domain and red-team evaluations with correct metrics, overlap analysis and uncertainty.

    20 min read
  343. ·machine learning

    KV Cache Deep Dive: Correctness, Memory and Serving Budgets

    Test exact cached decoding and grouped-query attention, derive byte budgets, and distinguish paging, precision and eviction.

    20 min read
  344. ·machine learning

    Quantization — INT8, INT4, GPTQ, AWQ

    Compute quantization error and metadata costs, distinguish compression algorithms and kernels, and design a complete local-artifact benchmark.

    17 min read
  345. ·machine learning

    Pruning and Distillation: Exact Masks and Correct Token Losses

    Implement exact pruning masks and shifted masked distillation, derive temperature gradients, and evaluate compression tradeoffs.

    20 min read
  346. ·machine learning

    Speculative Decoding — Acceptance, Residual Sampling and Cost

    Prove speculative sampling, implement bounded greedy and stochastic decoders, and compare proposal families with a measured runtime cost model.

    17 min read
  347. ·machine learning

    Continuous Batching: Scheduling, Cache Admission and Capacity

    Trace static and continuous batches, enforce cache admission, derive Little’s law and diagnose latency-throughput tradeoffs.

    20 min read
  348. ·machine learning

    Inside vLLM and TGI: Paging, Versioned Schedulers and Operations

    Implement a reference-counted block allocator, inspect pinned vLLM internals, and prepare honest serving and observability recipes.

    20 min read
  349. ·machine learning

    Deploying an LLM API: Bounded FastAPI Streaming and Lifecycle

    Preserve SSE framing, bound admission, authenticate and clean up streaming requests, and design deployment, retry and usage contracts.

    20 min read
  350. ·machine learning

    Latency vs Throughput — Little's Law, TTFT, ITL, and Load Testing

    Define honest streaming metrics, derive capacity and test SLO measurement with bounded load-test references.

    16 min read
  351. ·machine learning

    Multimodal — CLIP → LLaVA

    Derive contrastive learning and visual-token interfaces, train a synthetic dual encoder and design a complete multimodal evaluation.

    15 min read
  352. ·machine learning

    Agents and Tool Use

    Build a bounded tool controller with validated proposals, independent authorization, recovery and task-level evaluation.

    15 min read
  353. ·machine learning

    RAG as a testable evidence pipeline, not a truth switch

    Implement chunking, exact retrieval and rank fusion, integrate evidence packing and evaluate a complete RAG pipeline.

    18 min read
  354. ·machine learning

    Mixture of Experts (MoE) Intuition

    Implement sparse expert routing, derive parameter and memory accounting, and test load-balancing and dispatch assumptions.

    15 min read
  355. ·machine learning

    Long Context — RoPE Scaling, YaRN, ALiBi

    Derive RoPE extension, YaRN scaling and ALiBi, then evaluate long-context systems without confusing acceptance with recall.

    15 min read
  356. ·machine learning

    Red-Team + Safety Eval

    Design controlled safety tests, separate harm from refusal, and connect system controls to evidence-based release decisions.

    15 min read
  357. ·machine learning

    Capstone: a reproducible model-and-evidence laboratory

    Complete a reproducible CPU laboratory or a fully specified 100M training and release project with explicit evidence gates.

    19 min read
  358. ·cloud engineering

    Ship It — Deploy, Package, Sustain

    Choose a route from local Python to an API, from an app to a container, or from a binary to a Windows package—and build a repeatable review and learning habit.

    8 min read
  359. ·machine learning

    Stanford CS229: Machine Learning Course

    A source-reviewed CS229 orientation with worked linear algebra, probability, optimization and runnable algorithm fixtures.

    17 min read
  360. ·systems

    The 6-Month Learning Plan · 130 Sessions and a Foundations Lab

    A coherent 130-session, 16-module engineering curriculum with 26 revisions, a protected ten-lesson Foundations Lab and honest pacing and prerequisite boundaries.

    30 min read
  361. ·application engineering

    MS Stack Ch 22 — Pro skills (the bits no one writes down)

    Code review craft, on-call composure, incident writing, technical proposals, mentoring, learning velocity, knowing when to rewrite. The chapter that turns a strong engineer into a senior one.

    31 min read
  362. ·application engineering

    MS Stack Ch 21 — Testing strategy

    Unit, integration, end-to-end, contract, mutation, load — the testing pyramid for ASP.NET Core + React on Azure. xUnit, WebApplicationFactory, Vitest, Playwright, k6, Stryker, Pact.

    30 min read
  363. ·application engineering

    MS Stack Ch 12 — KQL contracts, joins and telemetry

    Read KQL pipelines, preserve join and time-window semantics, design bounded telemetry queries, and separate parameter binding, authorization and query cost.

    35 min read
  364. ·application engineering

    From Novice to Fluent on the Modern Microsoft Web Stack — 22-Chapter Self-Study Plan

    An opinionated 22-chapter self-study plan from zero to fluent on the modern Microsoft web stack: PowerShell + .NET + ASP.NET Core + React + TypeScript + Azure + KQL + Polly + Bicep — with worked examples, failure analysis and practice.

    9 min read
  365. ·application engineering

    MS Stack Ch 1 — Developer tooling

    PowerShell, Git's three trees, VS Code, browser DevTools, and the package managers that run your day. The boring tools that determine whether you'll feel fluent or fighting for the next two years.

    29 min read
  366. ·application engineering

    MS Stack Ch 2 — Web fundamentals

    HTTP, headers, cookies, TLS, REST, CORS, JSON — the wire-level protocol every backend and frontend bug eventually reduces to. Buy yourself fluency in the protocol and stop guessing.

    30 min read
  367. ·application engineering

    MS Stack Ch 3 — C# language

    C# 12 + .NET 8: the type system, LINQ, generics, async/await, pattern matching, records, nullable reference types. The language you'll write 1000s of lines of in production.

    26 min read
  368. ·application engineering

    MS Stack Ch 4 — .NET runtime and async

    The CLR, garbage collector, Task vs ValueTask, the async state machine, cancellation, the dotnet CLI, NuGet, global.json, central package management — the runtime your C# code actually lives in.

    27 min read
  369. ·application engineering

    MS Stack Ch 5 — ASP.NET Core

    Minimal hosting, dependency injection, middleware, routing, configuration, options, model binding, ProblemDetails, BackgroundService, health checks. The web framework you'll spend the next decade in.

    25 min read
  370. ·application engineering

    MS Stack Ch 6 — Modern frontend baseline

    Semantic HTML, ARIA + a11y, the CSS cascade + box model + Flexbox + Grid, modern JavaScript (ES2024), fetch, the event loop. The browser-side foundations every React app stands on.

    39 min read
  371. ·application engineering

    MS Stack Ch 7 — TypeScript

    Structural typing, narrowing, generics, discriminated unions, utility types, tsconfig. TypeScript without the over-engineering.

    39 min read
  372. ·application engineering

    MS Stack Ch 8 — Frontend build tooling

    Vite, HMR, Rollup, esbuild, npm vs pnpm, tree-shaking, env vars, dev proxy. Understanding what your bundler is actually doing so when it breaks, you know where to look.

    36 min read
  373. ·application engineering

    MS Stack Ch 9 — React

    Components, JSX, the rendering model, hooks (useState, useEffect, useMemo, useCallback, useRef, useReducer, useContext), custom hooks, error boundaries, Suspense, wrapping imperative libraries. React without the cargo cult.

    34 min read
  374. ·application engineering

    MS Stack Ch 10 — Routing and state in SPAs

    React Router (nested + lazy), URL as state with useSearchParams, server state vs UI state, TanStack Query, Zustand vs Redux Toolkit. Choose your state strategy deliberately.

    26 min read
  375. ·application engineering

    MS Stack Ch 11 — Data visualisation with Highcharts

    Highcharts options model, series types, axes, performance for high-cardinality data, theming, accessibility, exporting. A versioned charting model for enterprise dashboards.

    28 min read
  376. ·application engineering

    MS Stack Ch 13 — Azure App Service

    App Service plans, deployment slots + swap + warmup, app settings, Key Vault references, VNet integration, scale-out rules, custom domains + TLS. The Microsoft PaaS that hosts most of the stack.

    27 min read
  377. ·application engineering

    MS Stack Ch 14 — Identity for cloud apps

    Entra ID, OAuth 2.0 + OIDC, Easy Auth (App Service Authentication), Managed Identity, On-Behalf-Of flow, certificate-based authentication. The identity stack that lets you stop storing passwords or secrets.

    27 min read
  378. ·application engineering

    MS Stack Ch 15 — Observability

    Serilog structured logging, Application Insights, OpenTelemetry, correlation IDs, distributed tracing, KQL queries for telemetry, alerts, dashboards. Knowing what your app is doing in production.

    22 min read
  379. ·application engineering

    MS Stack Ch 16 — Resilience patterns with Polly v8

    Retry with jittered backoff, timeout, circuit breaker, bulkhead, fallback, rate-limiter, hedging — composed into a single resilience pipeline. The patterns that keep your app alive when downstream services don't.

    23 min read
  380. ·application engineering

    MS Stack Ch 17 — Caching

    IMemoryCache, IDistributedCache, HybridCache (.NET 9), Redis, cache-aside, write-through, stampede protection, invalidation, TTL strategies. Freshness, isolation and load control without invented speed guarantees.

    25 min read
  381. ·application engineering

    MS Stack Ch 18 — CI/CD with Azure DevOps

    YAML pipelines, templates + parameters + extends, agent pools, federated identity for Azure deploys, SDL gates (CodeQL, credential scanner, container scanning), multi-stage deploys, environments + approvals.

    36 min read
  382. ·application engineering

    MS Stack Ch 19 — IaC and rollout orchestration

    Bicep modules, what-if previews, environments, region rollouts. Awareness of Ev2 (Microsoft internal), Spinnaker, ArgoCD. The pattern for safely deploying infrastructure + apps across regions.

    30 min read
  383. ·application engineering

    MS Stack Ch 20 — Security baseline

    OWASP Top 10, secrets management, transport security, auth hardening, supply-chain integrity, input validation, output encoding, security headers. The non-negotiable security checklist for every web app.

    24 min read
  384. ·cloud engineering

    Automating audio generation

    From text , generate audio files and publishing them to webapp

    13 min read
  385. ·cloud engineering

    Deploying scripts as an API in Azure

    Deploying local python scripts and converting them as an API.

    9 min read
  386. ·cloud engineering

    Building windows app and publishing to app store.

    Exploring the fundamentals of building an .exe file from scratch, including C++ compilation, object files, linking, DLLs, and more.

    10 min read
  387. ·cloud engineering

    Basics of Azure AI Foundry

    A self-sufficient guide to Azure AI Foundry — what it is, how the hub/project/deployment model works, how to ship a grounded agent end-to-end with SDK + Bicep, and the security/eval/cost levers you cannot skip.

    12 min read
  388. ·cloud engineering

    Taking the Azure Fabric Ignite Edition Challenges to Complete

    Microsoft Learn Challenge conducting a challenge to get good in few of the challenges which are super useful to complete to gain knowledge on Microsoft Fabric.

    23 min read
  389. ·cloud engineering

    Exploring different services in GCP

    Exploration and documentation of different services offered in GCP

    22 min read
  390. ·application engineering

    Starting a company in India — a planning journal, corrected

    Tech Vistara's recorded domain and landing-page work, with a source-checked comparison of entity structures, incorporation, tax, recognition, IP and operating controls. Proposed steps remain proposed.

    26 min read
  391. ·cloud engineering

    Exploring Azure Data Explorer and Best Practices

    A self-sufficient deep-dive on Azure Data Explorer (ADX/Kusto) — architecture, the KQL language from zero to advanced, ingestion patterns, performance/cost levers, and operational best practices.

    16 min read
  392. ·cloud engineering

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