The breaker as a state machine that stops calling a failing dependency: closed, open and half-open; choosing rate windows versus consecutive failures; recovery probe limits and in-flight work across state transitions; the failure predicate—classifying correlated dependency failures rather than blindly counting status classes—and the distinction between protecting caller resources by failing fast and providing a semantically valid fallback. Use when a breaker trips on consecutive failures, when it never trips or trips on one client's bad requests, when half-open sends full traffic at a recovering dependency, when a breaker sits on a call with no timeout under it, or when a…
