Backend
What is Circuit Breaker?
A resilience pattern that stops calls to a failing dependency, failing fast until the service recovers, preventing cascading failures.
Definition
The circuit breaker pattern wraps calls to a remote dependency and tracks failures. While healthy, the circuit is closed and calls pass through. Once errors cross a threshold, it opens: calls fail immediately without touching the struggling service, giving it room to recover instead of drowning it in retries. After a cooldown, a half-open state lets a few probe requests through; success closes the circuit again. Resilience4j, Polly (.NET), and Envoy's outlier detection implement it. Breakers pair naturally with timeouts, retries, and fallback responses in distributed systems.