Systematic test pyramid breakdown: bottom unit tests (many, fast, mock isolated), middle integration tests (real service/db/message interaction), top E2E tests (few, critical user flows). Recommended ratio 70/20/10, with coverage metrics and implementation playbook.
Master DP: 5-step universal framework then 5 high-frequency templates: Knapsack, Subsequence, Interval DP, Bitmask DP, Tree DP, each with canonical code and variant keys.
Advanced patterns: CQRS separate read/write models for query performance; Event Sourcing using events as source of truth for audit + time travel. Covers consistency, snapshots, idempotency pitfalls and anti-patterns.
Complete Go native concurrency guide: lightweight goroutines, CSP-style channels, sync.WaitGroup, Context cancellation, worker pool patterns, and goroutine leak prevention.
Master Rust's most unique concepts: ownership rules, mutable/immutable borrowing constraints, lifetime annotations. Compile-error examples + fixes to think like the Borrow Checker for safe zero-cost code.
Deep Python concurrency comparison: ThreadPool for IO-bound, ProcessPool bypassing GIL for CPU-bound, asyncio coroutines for ultra IO. 4-dimension decision tree with perf and complexity.
Three core caching patterns: Cache-Aside consistency, Write-Through atomic updates, Write-Behind async high-throughput writes, plus solutions for stampede, penetration, and avalanche.
Master PostgreSQL optimization: EXPLAIN ANALYZE plans, choosing index types (B-tree/GIN/BRIN), updating statistics, tuning joins, and partitioned table design for maximum performance.
