Circuit Breaker Pattern:?

Short answer: A circuit breaker monitors failures and trips (opens) if a service experiences repeated failures, preventing further calls to the failing service and giving it time to recover. Tools: Hystrix, Resilience4j.

Real-world example (ShopNest)

If Payment is down, the Order service fails fast with a circuit breaker instead of hanging every checkout thread.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.