Reliability

How to diagnose flaky integration tests in CI: shared state, timing assumptions, parallel worker conflicts, database cleanup gaps, and unstable dependencies.

How to plan database migration rollback in production with compatibility windows, forward fixes, backfill recovery, and clear stop points.

How database connection pool exhaustion happens under load, how to tell pool wait from slow SQL, and how to size pools across instances safely.

How retry budgets keep microservice retries useful without amplifying overload: per-request limits, client retry ratios, token buckets, and metrics.

Observability vs logging in production, with a practical guide to when logs, metrics, traces, and correlation IDs answer different debugging questions.