Building Resilient Microservices with Circuit Breakers in Node.js

Building Resilient Microservices with Circuit Breakers in Node.js Microservices fail. Not if — when. A database goes down, a third-party API rate-limits you, a downstream service redeploys and spends 30 seconds restarting. What separates resilient systems from fragile ones is not preventing these failures but containing them. The circuit breaker pattern is the most battle-tested tool for that job. In this article you'll implement circuit breakers in Node.js using the opossum library — the de facto standard in the Node ecosystem. You'll cover the three states of a circuit breaker, timeout and threshold configuration, fallback strategies, integration with metrics and alerting, and a testing strategy that validates failure behaviour without relying on actual network outages. All examples use Node.js 20 LTS and TypeScript-friendly patterns. The code is production-ready. Why Circuit Breakers Exist Imagine a payments service that calls an upstream fraud-detection API. The fraud API starts re