Lesson 20 — Circuit breaker

Stop calling what is broken

If a service you depend on is down, waiting for each call to time out makes your service slow too. A circuit breaker counts failures; after max failures in a row it opens and fails fast without calling at all. (The name comes from the electrical switch that cuts power to protect a circuit.)

Note: real DevOps tools (CI servers, load balancers, Docker, Kubernetes) cannot run in your browser, so this exercise is a small plain-JS simulation of the logic those tools use. ok stands for whether the real call would have succeeded.

Why it matters: it stops one broken service from dragging down everything that calls it.