18. Final Tips

Senior-level habits that demonstrate ownership, clarity, and sound trade-offs.

• Lead with the answer; justify briefly.
• State trade-offs explicitly (GIL: threads for I/O, processes for CPU).
• Pick the right concurrency primitive; never block the asyncio event loop.
• Always set timeouts and use retries with jitter for network calls.
• Quantify assumptions (latency, throughput, expected scale).
• Log structured JSON with correlation IDs; never log secrets or PII.
• Use specific exceptions and raise ... from e for causal context.
• Validate inputs and schemas at the boundaries of your system.
• Design idempotent writes; use Idempotency-Key for POST; standardize error payloads.
• Prevent ORM N+1 with eager loading; use pooling; keep transactions short.
• Cache intentionally; pick an eviction strategy; prevent stampedes (jitter, single-flight).
• Measure before optimizing; profile CPU, I/O, and memory separately.
• Prefer composition over inheritance; keep functions small and pure.
• Use context managers for resources; implement graceful shutdown on SIGTERM.
• Document decisions; keep config in env; automate checks in CI.