A backend engineer shares a real incident where an internal API became unreliable, failing most of the time due to timeout errors. The investigation revealed thread pool exhaustion, improper timeout settings, and lock contention as root causes. The post details step-by-step debugging using thread dumps, log analysis, and load testing. Key fixes included adjusting thread pool sizes, optimizing lock granularity, and setting appropriate client-side timeouts. This case study is a practical reference for engineers facing similar concurrency-related performance degradation in production systems. It emphasizes the importance of systematic debugging over guesswork and highlights common pitfalls in concurrent service design.
A detailed walkthrough of diagnosing and fixing intermittent API timeouts caused by concurrency issues in a backend service.