Circuit Breaker
Stop calling a failing dependency; fail fast, probe for recovery — the pattern that prevents cascade failures.
A circuit breaker watches calls to a dependency. Too many failures → the breaker opens and calls fail instantly (or fall back) instead of stacking up timeouts. After a cooldown it goes half-open, letting probe requests test recovery before closing again. It protects both sides: your threads aren’t blocked, and the struggling service isn’t hammered while it heals. Pairs with retries-with-backoff and backpressure.