Circuit Breaker — Fail Fast

09 · Resilience Pattern

Circuit Breaker — Fail Fast

When a service keeps failing, stop sending requests — return an error immediately instead of waiting. Prevents cascade failures. Named after electrical circuit breakers.

CLOSED

🟢

Normal operation

Requests flow through normally. Failure counter monitored. If failures exceed threshold → OPEN.

→

OPEN

🔴

All requests blocked

No requests sent downstream. Returns error immediately. Waits timeout period → HALF-OPEN.

→

HALF-OPEN

🟡

Testing recovery

Allows limited test requests. Success → CLOSED again. Failure → back to OPEN.

Used by: Netflix Hystrix, AWS SDK, Resilience4j, Polly (.NET). Prevents one failing service from cascading and taking down your entire system.

● ANIMATED FLOW