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Changelog

This file records meaningful content and validation changes to the placement preparation book. Dates use the project timezone, Asia/Calcutta.

2026-08-13 — Software Engineering: dedicated Testing, DevOps, and Contributing pages

  • Added software-engineering/testing.md (levels, types, TDD/BDD, strategy), software-engineering/devops.md (CI/CD, deployment strategies, IaC), and software-engineering/CONTRIBUTING.md (contribution guide).
  • Registered all three in SUMMARY.md; re-pointed the Software Engineering README and documentation.md links to the new local pages (previously routed to ../testing/README.md, ../cloud/cicd/README.md, and a GitHub URL).
  • Validation after change: 0 broken links, Summary navigation OK, MathJax OK, Mermaid heuristic 4,405/4,405.
  • Committed on dev as 6318d8b and pushed to origin/dev; main unchanged.

2026-08-13 — Pull and topic-completeness audit

  • Fast-forwarded local dev to remote commit 61ac3ce.
  • Found ten Summary entries whose target files were absent and added concise, referenced pages for data formats, data quality, search fundamentals, vector search, technical interviews, group discussions, SQL window functions, joins, DBMS concurrency scenarios, and testing interview questions.
  • Repaired four stale links in Software Engineering and testing documentation.
  • Validation after repair: 0 broken links, complete Summary reachability, MathJax OK, Mermaid 4,405/4,405, and Mermaid v11 parser 4,405/4,405.
  • Work remains on dev; main was not modified.

2026-08-13 — Massive content expansion (parallel agents)

Six parallel agents are creating comprehensive new sections:

Git Section (15 files)

  • src/git/README.md — Overview and chapter outline
  • src/git/internals.md — Objects (blob, tree, commit, tag), refs, HEAD, index, packfiles, SHA-1
  • src/git/fundamentals.md — Setup, config, staging, committing, diffing, undoing
  • src/git/branching.md — Branches, fast-forward, three-way merge, conflicts, octopus merge
  • src/git/rebasing.md — Rebase, interactive rebase, –onto, autosquash, rerere
  • src/git/stashing.md — Stash operations, partial stashing, branch from stash
  • src/git/advanced.md — cherry-pick, revert, reset, reflog, bisect, worktree, submodule, blame, grep
  • src/git/remotes.md — fetch, pull, push, force-with-lease, multiple remotes
  • src/git/tags.md — Lightweight vs annotated, semver, GPG signing
  • src/git/hooks.md — Client-side (pre-commit, commit-msg, pre-push), server-side (pre-receive, update)
  • src/git/workflows.md — Trunk-based, GitFlow, GitHub Flow, GitLab Flow, forking
  • src/git/github.md — PRs, code review, branch protection, CODEOWNERS, GitHub Actions
  • src/git/interview-questions.md — 25+ questions from beginner to advanced + scenarios
  • src/git/cheat-sheet.md — Quick reference for all commands

Software Engineering Section (10 files)

  • SDLC models, Agile/Scrum, requirements engineering, software design (SOLID)
  • Code quality, documentation, project management, metrics, team dynamics
  • Interview questions covering all SE topics

Programming Fundamentals Section (10 files)

  • Variables/types, scope/lifetime, functions (closures, HOFs, generators)
  • Error handling, type systems, memory model, I/O/serialization
  • Modules/packages, interview questions

Aptitude & Placement Preparation (17 files)

  • Quantitative: percentages, ratios, averages, profit/loss, time/work, speed/distance
  • Logical: probability, number systems, logical reasoning, data interpretation
  • Placement: campus process, online assessment, technical/HR interview, group discussion

Resume, Behavioral, Communication (15 files)

  • Resume: structure, bullet writing, projects, technical skills, ATS optimization
  • Behavioral: STAR method, 30+ common questions, company fit, scenarios
  • Communication: technical, interview, written

Machine Coding & Practical Problems (22 files)

  • Machine coding: parking lot, elevator, library, splitwise, rate limiter, LRU cache, task scheduler
  • Practical problems: parsers, CLI tools, file processing, concurrent problems, system utilities
  • DBMS interview problems: classic SQL, window functions, joins, optimization, concurrency

Security, Data Engineering, Search (18 files)

  • Security: authentication (OAuth/OIDC/JWT), authorization (RBAC/ABAC), web security (OWASP Top 10)
  • Cryptography: AES/RSA/ECC, TLS, password hashing, certificates, PKI
  • Data engineering: Spark, Kafka, Airflow, Parquet/Avro/ORC, data quality
  • Search: inverted indexes, TF-IDF/BM25, Elasticsearch, vector search

2026-08-12 — Research loop batch 4

  • Added backend/api/graphql-federation.md with entities, composition, directives, query planning, schema governance, and failure modes.
  • Added distributed/fundamentals/distributed-locks.md with lease races, fencing tokens, Redis/Redlock, ZooKeeper, etcd, and lock alternatives.
  • Added storage/tiered-storage.md with hot/warm/cold policies, RocksDB tiering, object lifecycle, caching, cost, latency, and recovery trade-offs.
  • Added navigation, cross-reference edges, backlog markers, and coverage data for the research batch.

2026-08-12 — Research loop batch 3

  • Added networks/ebpf-networking.md using Linux kernel networking/BPF docs, AF_XDP, XSKMAP, SOCKMAP, BPF maps, Cilium, and eBPF Docs references.
  • Added languages/rust/async-runtimes.md using the Rust Async Book, Tokio, smol, async-std, Glommio, Monoio, and Embassy documentation.
  • Added backend/observability/opentelemetry.md using OpenTelemetry signal, propagation, semantic-convention, sampling, and specification docs.
  • Added Summary links, graph edges, backlog markers, and coverage updates.

2026-08-12 — Research loop batch 2

  • Added storage/nvmeof.md using current NVM Express TCP/RDMA transport specifications and Linux NVMe documentation.
  • Added distributed/fundamentals/crdts.md using CRDT.tech, the CRDT papers bibliography, the original CRDT literature, and Ink & Switch local-first and Peritext research.
  • Added backend/patterns/cdc-outbox.md using current Debezium connector, Outbox Event Router, PostgreSQL logical decoding, and Microservices.io transaction-log-tailing documentation.
  • Added Summary links, cross-reference edges, backlog completion markers, and coverage updates for all three topics.

2026-08-12 — Research: ABA and safe memory reclamation

  • Added src/concurrency/aba-problem.md covering ABA interleavings, tagged pointers, hazard pointers, epoch-based reclamation, RCU, reference counting, memory ordering, implementation choices, and interview questions.
  • Cross-linked the chapter to lock-free structures, the memory model, Linux RCU, OS memory barriers, C++, Rust/Crossbeam, and DSA hardware context.
  • Researched against Linux RCU Concepts, WG21 P2530R3, WG21 P2545R4, the current C++ working draft, IBM’s hazard-pointer paper, Boost.Lockfree, Folly Hazptr, and Crossbeam Epoch.

2026-08-12 — Add MathJax validation tooling

  • Added scripts/check-mathjax.py to verify mathjax-support = true, balanced escaped inline/block delimiters, no legacy $$ delimiters outside code, and no unclosed Markdown fences.
  • Added optional --book-dir checking for the generated MathJax runtime.
  • Added the MathJax check as step 6 in scripts/validate-all.sh and documented standalone usage in scripts/README.md.

2026-08-12 — Research and validation audit

Fixed

  • Converted legacy $$...$$ display equations in 61 Markdown pages to the mdBook-compatible escaped block delimiters used by MathJax.
  • Closed malformed code fences in DSA advanced segment trees, Linux firewall maps, and ML optimizer examples.
  • Repaired nine stale internal heading fragments and four escaped Ctrl+ code examples discovered by the audit.
  • Corrected the retired ebpf.io/docs URL to the maintained docs.ebpf.io documentation site.

Audit result

  • Broken relative links: 0.
  • SUMMARY reachability: 1,533 of 1,533 content pages linked.
  • Mermaid heuristic/parser: 4,387 / 4,387 passed.
  • Math delimiter counts are balanced outside fenced code and inline code spans.
  • No exact duplicate Markdown bodies were found.
  • 73 URL-bearing pages without a References-style heading and 112 pages with no content cross-links remain as research-review candidates; they are not navigation failures because Summary reachability is complete.

2026-08-12 — Enable MathJax and automatic cross-reference graph

  • Enabled mdBook’s built-in MathJax support with output.html.mathjax-support = true.
  • Added scripts/generate-cross-reference-graph.py and a Meta navigation page; the GitHub Pages workflow now generates the interactive graph automatically after every successful mdBook build.
  • Added the Cross-Reference Graph Meta page; the generated view is output-only and is not committed as a large artifact.
  • Confirmed the integrated DSA source uses mdBook-compatible escaped inline mdBook-compatible inline and block delimiters.
  • The generated DSA math page now includes the MathJax runtime instead of leaving formulas as raw delimiter text.

2026-08-12 — Linux and DSA book integration

Added

  • Integrated the educational Markdown from lb2 into the navigable src/linux/ Linux deep-dive track.
  • Integrated the educational Markdown from dsa_book_2 into the navigable src/dsa/ DSA track.
  • Added a referenced Linux Tools for Placement Preparation chapter covering file/text, process, storage, networking, debugging, and developer-workflow tools.
  • Added explicit project status, progress, backlog, coverage, and knowledge graph tracking for this batch.

Fixed

  • Rewrote imported relative Markdown links for their final locations and removed stale source-only targets rather than leaving broken navigation.
  • Repaired 34 imported Mermaid diagrams identified by the repository heuristic validator, including unsafe labels, malformed subgraphs, sequence syntax, and a corrupted routing diagram.
  • Repaired 15 parser-only Mermaid failures found by Mermaid v11, including nested quotes, multiline labels, invalid state transitions, inline comments, reserved node IDs, and source-file line-join corruption.
  • Added five Linux build chapters that were initially hidden by the target repository’s generic build/ ignore rule.

Validation

  • Link checker: 0 broken links.
  • SUMMARY checker: OK for 1,534 Markdown files (1,533 linked chapters).
  • Mermaid heuristic: 4,387 / 4,387 passed.
  • Mermaid v11 parser: 4,387 / 4,387 passed.
  • validate-all.sh: exit 0 / ALL VALIDATION PASSED when called with an absolute repository path.
  • mdBook 0.4.52: a full search-disabled build produced 1,575 output files successfully; the normal search-enabled build was killed by the sandbox memory limit with exit 137. The production configuration remains unchanged.

Git

  • Integration commits 42c4e57 and 5f986da, followed by metadata/validation commit 79145d7, were made on dev and pushed to origin/dev.
  • The validated tree was promoted from dev to main and synchronized back to dev; both release branches are kept aligned.
  • The working tree was clean after promotion.

Earlier history

See the preceding commits for the existing autonomous content-expansion batches. This changelog intentionally records the current integration batch without rewriting that history.

2026-08-15 — Massive advanced topics expansion (1,500+ topics across 20 sections)

Two commits pushed to origin/dev:

  1. docs: add 1,500+ advanced topics across 20 sections (A-T) (fa3dc05) — 131 new markdown files across 20 directories covering topics 1-1500 from the master specification. ~249K words total. Sections: Advanced OS, Linux Kernel, Distributed Systems, Distributed Storage, Advanced DBs, Advanced Algorithms, PL/Compilers, Computer Architecture, HPC, Networking Research, Formal Methods, Security Research, Blockchain, AI Systems, AI+Distributed, Cloud/Serverless, Edge/IoT, Quantum Computing, Supply Chain/Build Systems, Observability.
  2. fix: resolve all validation errors and add gap content (3c41f0b) — Added Build-It-Yourself track (34 implementation projects across 5 domains), Advanced Benchmarking section (methodology, pitfalls, statistics, tools, flame graphs), fixed 3 missing topics (hugetlbfs, TCP autotuning, zk-rollups), fixed 3 missing SUMMARY entries, 11 broken links, 13 mermaid errors, 3 legacy MathJax delimiters, 6 unclosed code fences, 26 single-backslash delimiters.

Validation after expansion

  • Link checker: 0 broken links
  • SUMMARY checker: OK (2,117 content files, all reachable)
  • Mermaid heuristic: 4,883 / 4,883 passed (100%) — 478 new diagrams
  • MathJax: OK (0 legacy delimiters, 0 unclosed fences, 0 unbalanced)

Every commit was preceded by a clean validation run. main unchanged; all work on dev.

2026-08-15 — OpenClaw expansion batch

Five focused commits pushed to origin/dev:

  1. docs(index): add master topic index as authoritative roadmap — src/index.md (1 660 lines, 50 topic sections) added; wired into SUMMARY.md top nav and Meta section.
  2. docs(java): expand virtual-threads page with depth — src/languages/java/virtual-threads.md 139 → 261 lines. JEP timeline, continuation-on-heap internals, structured-concurrency API churn, migration playbook, comparison vs goroutines / Kotlin coroutines / Reactor.
  3. docs(python): expand free-threaded page with depth — src/languages/python/free-threaded.md 148 → 235 lines. PEP 779, biased-locking internals, immortal objects, Py_BEGIN_CRITICAL_SECTION, Cython freethreading directive, runtime introspection, comparison vs Java Loom / Go / Ruby Ractor.
  4. docs(storage): expand Ceph CRUSH/RADOS deep dive — src/storage/ceph-crush.md 181 → 340 lines. Straw2 algorithm, CRUSH rules, upmap balancer, PG peering state machine, Bluestore internals, replication vs EC table, upper-layer services.
  5. docs(cs-theory): add formal methods page — new src/cs-theory/formal-methods.md (282 lines). TLA+, Alloy, Coq, Lean, Isabelle/HOL, Dafny, model checking, symbolic execution, abstract interpretation, distributed-systems verification, 8 interview questions.

Every commit was preceded by a clean mdbook build; no warnings introduced. token.txt is in .gitignore and was never staged.