Systems

How feature flags grow from safe release controls into hidden complexity, and how lifecycle rules, ownership, tests, and cleanup keep them contained.

Tests can pass while production still breaks when the suite proves the intended path but misses retries, concurrency, dirty data, rollout state, or ambiguous dependency behavior.

Why production caches return stale or contradictory data, including cache-aside races, invalidation gaps, TTL drift, local cache divergence, write-through trade-offs, and safer rollout checks.