What circuit breakers do
They sit between callers and an unhealthy service. When failures cluster, the breaker stops forwarding traffic.
Interactive Systems Explainers
Circuit Breaker Playground
See fast failure protect a recovering system.
Key Observations
What to Notice
Why fast failure helps
Rejected requests finish quickly. The service gets quiet space instead of another pile of slow waiting work.
Cascading overload
Without protection, traffic keeps entering a service that is already falling behind. Latency and failures feed each other.
Gradual recovery
Half-open lets a few test requests through. The breaker closes only after recovery looks steady.
Real-World Context
Circuit breakers are common around remote calls: payment providers, search services, recommendation APIs, internal microservices, and any dependency that can become slow or unavailable.
Their value is containment. One failing dependency should not consume threads, sockets, and user patience across the rest of the system. The tradeoff is deliberate refusal: some requests fail immediately so capacity is preserved and recovery has room to happen. Bad thresholds can flap, hiding real recovery or blocking healthy traffic too long during incidents and deploys.
Interactive Systems Explainers