16. Short Q&A Prompts

Senior drills to demonstrate depth, production realism, and crisp trade-off articulation.

• Explain G-M-P scheduling and how a blocking syscall is handled.

• Channels vs mutexes: when to prefer each and why?

• Show a bounded concurrency pattern (channel or x/sync/semaphore).

• Define the Go memory model's happens-before relation with a small example.

• Identify and fix a typed-nil error pitfall.

• Design idempotent write APIs with Idempotency-Key and dedup storage.

• Prevent cache stampede: lock, TTL jitter, refresh-ahead, single-flight.

• HTTP server hardening: which timeouts prevent slowloris and why?

• Tune http.Transport pools and timeouts for a busy downstream.

• gRPC reliability: deadlines, retries, backoff, and message size caps.

• Transactional Outbox: why it solves dual writes; outline the relayer.

• Detect and prevent goroutine leaks; where to check ctx.Done().

• Explain scheduler preemption and when to chunk CPU-heavy loops.

• sync.Map vs map+RWMutex: trade-offs and use cases.

• JSON performance: streaming, pooling, and codegen approaches.

• Histograms: pick buckets for a 200ms p99 SLO.

• JWT validation with JWKS rotation and kid cache.

• Conditional requests with ETag and 304 handling.

• Loop var capture in goroutines; show the correct pattern.

• Design a multi‑region active‑active data model and conflict resolution.

• Choose between a weighted semaphore and a bounded queue; justify backpressure.

• Explain Minimal Version Selection (MVS) and its impact on dependency upgrades.

• Container memory tuning: when to use GOMEMLIMIT vs GOGC.