Topic Backlog

Auto-maintained by research agents. Topics discovered during expansion that need coverage. Priority: HIGH (interview-critical) | MEDIUM (important) | LOW (nice-to-have) Last updated: 2026-08-16 (validation re-run, meta sync)

Dev pull audit — 2026-08-13

• Pulled the latest dev expansion and repaired ten missing Summary targets plus four stale relative links. All pulled pages are now Summary-reachable.
• Remaining work is content depth/references review, not broken navigation.

Software Engineering pages — 2026-08-13

• Added dedicated testing.md, devops.md, and CONTRIBUTING.md under src/software-engineering/ (previously those links were redirected to the general testing/ and cloud/cicd/ sections and a GitHub URL).

Integration completed — 2026-08-12

• Linux deep dive (lb2) — integrated 444 educational pages under src/linux/, with source navigation adapted to the parent Summary.
• Linux tools — added a focused guide for find, xargs, text filters, process/system-call tools, storage inspection, networking, HTTP debugging, SSH/rsync, jq, make, and tmux, including interview questions, safety notes, and official references.
• DSA track (dsa_book_2) — integrated 193 educational pages and appendices under src/dsa/, from foundations to advanced algorithms.
• Integrity gate — 0 broken links, Summary navigation OK, and 4,387/4,387 Mermaid diagrams pass both the heuristic and Mermaid v11 parser checks.

Completed (since 2026-08-05) — Updated 2026-08-13

The following previously-backlogged topics now have dedicated coverage:

• Languages: C (8 files incl. ecosystem), C++ (8 incl. ecosystem), Rust (9 + ecosystem), Java (incl. GC java/gc.md + ecosystem), Python (9 + ecosystem), Go (6 incl. scheduler 5 files → 6 with web-frameworks), JavaScript/Node/V8 (3 → expanded nodejs 414 lines, v8 363 lines), OCaml (incl. ecosystem/tooling), TypeScript (type system, generics), Go Web Frameworks (NEW 2026-08-09: Gin/Echo/Fiber comparison with prod benchmarks, allocation analysis, decision flowchart)
• Frameworks: Spring Boot, FastAPI, Django, Express.js, React, Next.js, Tokio, PyTorch, Vue & Angular (combined page exists, could split)
• Backend: REST, gRPC, GraphQL, JWT/OAuth/sessions, Docker, Kubernetes, CI/CD (GitHub Actions, GitOps), Redis, Kafka, RabbitMQ, NATS, service mesh (service-mesh.md + NEW xds-protocol.md 2026-08-08: ADS, LDS/RDS/CDS/EDS/SDS, protobuf not YAML, SotW vs Delta), event sourcing, CQRS, idempotency, webhooks, connection pools, testing, xDS Protocol (NEW)
• ML/LLM: Transformers, attention, GPT/BERT, fine-tuning, RLHF/DPO, inference optimization (KV cache, quantization, speculative decoding, batching), RAG, vector databases, LLM security (OWASP Top 10), distributed training (DDP/FSDP/ZeRO/TP/PP), diffusion, MoE, Probabilistic Data Structures (NEW 2026-08-09: Bloom 10 bits/elem @1%, HLL 12KB fixed ~2%, CMS overestimates, use cases Cassandra/Chrome/BigQuery)
• OS: eBPF, io_uring, Linux kernel internals, namespaces, cgroups v2, kernel modules (NEW 2026-08-08: LKM lifecycle, insmod/modprobe, params, sysfs, signing/taint), kernel tracing (NEW 2026-08-09: ftrace, kprobes/kretprobes 0.05us vs 0.5us, tracepoints, perf, eBPF bpftrace one-liners), RCU (NEW 2026-08-09: grace period, publish-subscribe, quiescent states, checklist)
• Networks: QUIC, HTTP/3 (http3.md), QPACK RFC 9204 (NEW 2026-08-08: static 99 vs dynamic table, encoder/decoder streams, RIC/Base, blocking), TLS deep dive (1.3 handshake, ECDHE, mTLS, CT), Bluetooth (NEW: PAN profiles), eBPF networking
• DBMS: query optimization (cost model, join algorithms), storage engines (WAL, LSM), distributed SQL (CockroachDB/TiDB/Spanner), OLTP vs OLAP, WAL (NEW 2026-08-09: LSN/pageLSN, ARIES 3 phases, CLR, group commit, fuzzy checkpoint), LSM Compaction (NEW 2026-08-09: leveled vs tiered vs hybrid, WA 10-30× leveled, RocksDB tuning knobs, SAG), Congestion Control Overview (NEW: congestion-control/README.md wired)
• Cloud: autoscaling, disaster recovery & multi-region, IAM & secrets management, Kubernetes operators, Kubernetes operators (already done)
• Arch: CUDA programming (parallelism/cuda.md), Modern Processors expanded (x86-64 Xeon/EPYC, ARM Neoverse, RISC-V) via dev merge
• Interview: streaming analytics pipeline system design (real-world/streaming-pipeline.md), Probabilistic Data Structures for System Design (NEW), real-world examples Netflix/Twitter/Uber/WhatsApp/YouTube/Instagram/Dropbox/Google Search/distributed lock
• Storage: HDD/SSD/NVMe/object/block/file/distributed/Ceph/erasure-coding (10 files) → 12 files with WAL + LSM Compaction + Bluetooth fix, still low coverage (45%)
• Concurrency: fork-join/thread-pools/producer-consumer/readers-writers/async-await/futures/coroutines/lock-free/transactional-memory/go-channels/rust-ownership/java/python-gil (14) → 15 with RCU, still low (48%)
• OOP: coupling, cohesion & design principles (lld/coupling-cohesion-principles.md)
• Security: TLS deep dive, mTLS, certificate transparency already; auth expanded (OAuth, JWT, session, mTLS)

NEWLY COMPLETED (2026-08-13 — Parallel Agent Batch)

Completely New Sections Added:

• Git ✅ src/git/ — 15 files: internals, fundamentals, branching, rebasing, stashing, advanced ops, remotes, tags, hooks, workflows, GitHub, interview questions, cheat sheet
• Software Engineering ✅ src/software-engineering/ — 10 files: SDLC, Agile, requirements, design (SOLID), code quality, documentation, project management, metrics, team dynamics
• Programming Fundamentals ✅ src/programming-fundamentals/ — 10 files: variables/types, scope/lifetime, functions, error handling, type systems, memory model, I/O, modules
• Security & Cryptography ✅ src/security/ — 7 files: authentication (OAuth/OIDC/JWT), authorization (RBAC/ABAC), web security (OWASP), cryptography (AES/RSA/TLS), secrets management
• Machine Coding ✅ src/machine-coding/ — 10 files: parking lot, elevator, library, splitwise, rate limiter, LRU cache, task scheduler
• Data Engineering ✅ src/data-engineering/ — 7 files: Spark, Kafka, Airflow, Parquet/Avro/ORC, data quality
• Search Engines ✅ src/search/ — 5 files: inverted indexes, TF-IDF/BM25, Elasticsearch, vector search
• Aptitude ✅ src/aptitude/ — 11 files: percentages, ratios, averages, profit/loss, time/work, speed/distance, probability, number systems, logical reasoning, data interpretation
• Placement Preparation ✅ src/placement-preparation/ — 6 files: campus process, OA, technical/HR interview, group discussion
• Resume & Career ✅ src/resume/ — 7 files: structure, bullet writing, projects, ATS optimization
• Behavioral Interviews ✅ src/behavioral-interviews/ — 5 files: STAR method, 30+ questions, company fit, scenarios
• Communication ✅ src/communication/ — 4 files: technical, interview, written communication
• Practical Programming Problems ✅ src/practical-problems/ — 6 files: parsers, CLI tools, file processing, concurrent problems
• DBMS Interview Problems ✅ src/dbms/interview-problems/ — 6 files: classic SQL, window functions, joins, optimization, concurrency

REMAINING — MEDIUM Priority (Updated)

Operating Systems — Partially Done

• Linux Kernel Modules — loading, unloading, parameters (covered briefly; expand into a page) ✅ Done os/kernel/modules.md
• Linux Tracing Deep Dive — ftrace, kprobes, perf, eBPF, and advanced tracing are covered in the integrated Linux track; an LTTng comparison remains optional
• Memory Barriers Deep Dive — C++20/Java/Go memory models (acquire/release, seq_cst) — dedicated page missing, currently in OS sync

Networks — Partially Done

• HTTP/3 QPACK — header compression specifics ✅ Done networks/http/qpack.md
• Service Mesh internals — Istio/Envoy xDS protocol, sidecar dataplane ✅ Done backend/containers/xds-protocol.md
• eBPF Networking Deep Dive ✅ Done networks/ebpf-networking.md (2026-08-12): XDP, TC, socket hooks, maps, AF_XDP, Cilium, CO-RE, and observability

Languages / Frameworks — Partially Done

• Go web frameworks — Gin/Echo/Fiber comparison ✅ Done languages/go/web-frameworks.md
• Rust Async Runtimes ✅ Done languages/rust/async-runtimes.md (2026-08-12): Tokio, smol, async-std, Glommio, Monoio, Embassy, blocking and cancellation
• Python Free-Threaded (3.13t) Deep Dive — GIL removal, free-threaded build
• Java Loom Virtual Threads — expand java.md with Project Loom

Backend / Storage / Concurrency — Newly Discovered

• Tiered Storage and Data Temperature ✅ Done storage/tiered-storage.md (2026-08-12): hot/warm/cold, RocksDB, object lifecycle, caches, recovery
• Storage: SSTable Format — data blocks, index, bloom, footer, compression ✅ Done storage/sstable.md (2026-08-09): BlockBasedTable diagram, Index/Bloom/Footer 48 bytes magic, partitioned index/filter, read path, compression
• Storage: BlobDB — separation of small vs large values ✅ Done storage/blobdb.md (2026-08-09): WiscKey, BlobIndex file_no/offset/size, GC age cutoff 0.25, WA 1.4-1.7 vs 6.1-6.8 75% lower, options enable_blob_files/min_blob_size
• Storage: Ceph CRUSH/RADOS Deep Dive — CRUSH algorithm, placement groups, RADOS (still TODO)
• Storage: NVMe over Fabrics ✅ Done storage/nvmeof.md (2026-08-12): TCP/RDMA, discovery, queues, multipathing, security, observability
• Concurrency: Work-Stealing Scheduler — Go scheduler work-stealing, Java ForkJoinPool, Rust Tokio ✅ Done concurrency/work-stealing.md (2026-08-09): LIFO owner head vs FIFO thief tail, Go GMP P local 256 + global, Java ForkJoinPool WorkQueue 4096, Tokio 256 ring + injection queue
• Concurrency: ABA Problem & Memory Reclamation ✅ Done concurrency/aba-problem.md (2026-08-12): tagged pointers, hazard pointers, EBR, RCU, reference counting, memory ordering, C++26 safe-reclamation references
• Concurrency: Memory Model — C++/Java/Go memory models, acquire/release, data races ✅ Done concurrency/memory-model.md (2026-08-09): TSO vs weak ARM, DRF-SC happens-before, C++11 6 orders, Java volatile total order vs VarHandle acq/rel, Go channel happens-before, Rust Send/Sync, store buffering litmus

Interview / System Design — Newly Discovered

• GraphQL Federation ✅ Done backend/api/graphql-federation.md (2026-08-12): entities, composition, directives, query planning, governance
• API Versioning Strategies — URL vs header vs content negotiation, Stripe example ✅ Done backend/api/versioning.md (2026-08-09): 6 strategies table, URL path safest default, date-based Stripe pinning compatibility layer, decision flowchart, Deprecation/Sunset headers
• Rate Limiting Algorithms Deep Dive — token bucket vs leaky bucket vs sliding window logs vs sliding window counter ✅ Done backend/api/rate-limiting.md (2026-08-09): 5 algos fixed vs sliding log O(n) exact vs sliding counter 2 keys ~1% err vs token bucket HASH burst vs leaky queue steady, comparison table, Redis Lua token bucket script, decision tree
• Distributed Lock Deep Dive ✅ Done distributed/fundamentals/distributed-locks.md (2026-08-12): leases, fencing tokens, Redis/Redlock, ZooKeeper, etcd, and alternatives
• Change Data Capture & Outbox Pattern ✅ Done backend/patterns/cdc-outbox.md (2026-08-12): dual-write failure, Debezium, WAL retention, idempotency, ordering

LOW Priority

• Quantum Computing — qubits, gates, algorithms (curiosity, not interview-critical)
• Blockchain — consensus PoW/PoS, smart contracts, Merkle trees (could be arch/blockchain.md or separate)
• Edge Computing — CDN compute, edge functions (covered in cdn/edge.md; could expand with Cloudflare Workers, Fastly Compute@Edge)
• Observability Deep Dive ✅ Done backend/observability/opentelemetry.md (2026-08-12): signals, propagation, Collector, semantic conventions, sampling, cardinality

NEWLY COMPLETED (2026-08-15 — OpenClaw expansion batch)

• Master topic index ✅ src/index.md — added the 1 660-line master topic database that was previously missing from the repo, covering all 50 sections from Algorithms through Interview Meta Topics. Wired into SUMMARY.md at the top navigation and the Meta section.
• Java Virtual Threads deep dive ✅ src/languages/java/virtual-threads.md expanded from 139 → 261 lines. Added JEP timeline (JDK 19 through 25), continuation- on-heap internals, three creation patterns, structured-concurrency API churn note (JEP 499 / 505), scoped-values rationale, migration playbook, comparison table vs goroutines / Kotlin coroutines / Reactor, 8 interview questions.
• Python Free-Threaded deep dive ✅ src/languages/python/free-threaded.md expanded from 148 → 235 lines. Added PEP 779, biased-locking internals, immortal objects (PEP 683), per-object critical sections (Py_BEGIN_CRITICAL_SECTION), Cython freethreading=True directive, C-extension compatibility table, runtime introspection (sys._is_gil_enabled, -X gil=0), comparison vs Java Loom / Go / Ruby Ractor, 7 interview questions.
• Ceph CRUSH/RADOS deep dive ✅ src/storage/ceph-crush.md expanded from 181 → 340 lines. Added straw2 bucket algorithm explanation, CRUSH rule step semantics, upmap balancer override, PG peering state machine (Mermaid state diagram), Bluestore internals (WAL/BlockDB/blob sharing), replication vs erasure coding table, upper-layer services (RBD/CephFS/RGW), performance characteristics, comparison vs HDFS/MinIO/S3, 9 interview questions, references to Weil SC 2006 paper and doctoral dissertation.
• Formal Methods ✅ src/cs-theory/formal-methods.md — new 282-line page covering index.md Section 36. TLA+ (with Counter example, AWS DynamoDB case study), Alloy (with file-system example), Coq (CompCert, Four Colour Theorem), Lean (Mathlib, Verdi), Isabelle/HOL (seL4), Dafny (binary search auto-active verification), model checking (BDD, BMC, partial-order, symmetry), symbolic execution (KLEE/angr/SAGE), abstract interpretation (Astrée, Rust borrow checker), distributed-systems verification workflow, trade-offs table, 8 interview questions.

Decisions / Notes

• Keep autonomous loop adding topics based on coverage lowest first: Storage (45%) and Concurrency (48%) still lowest → prioritize WAL, LSM compaction (done), next SSTable, BlobDB, RCU (done), memory barriers, work-stealing.
• After storage/concurrency reaches 60%, move to Frameworks (60%) and Distributed (55%) and Cloud (60%)
• Update knowledge graph each batch to keep cross-links
• Maintain 100% mermaid pass, 0 broken links, build clean — fix regressions immediately after merging dev
• Next candidates: Serialization (index §39, partially covered — protobuf/Avro/Cap’n Proto comparison page would unify scattered content); API versioning is already covered; Quantum Computing (§35) is low-priority.

NEWLY COMPLETED (2026-08-15 — Parallel Agent Waves 1-4)

Four waves of parallel agents (7+7+7+4 = 25 agents) closed all 25 previously-missing section-level pages, covering all 50 sections of src/index.md. Each new page is a section-level integrator covering that section’s topics, with Mermaid diagrams, comparison tables, interview questions, and authoritative references.

Total new content: ~11,500 lines across 25 new pages.

All 50 sections of index.md now have dedicated coverage. Full validation suite passes: 0 broken links, SUMMARY navigation OK, MathJax balanced, Mermaid 100%.