lightbulbBook reference: Beyond the books. Original notes kept below; rewrite them in your own words.
3.2.1 Circuit Breakers
When error rate or latency crosses a threshold, the breaker opens: calls fail immediately (or hit a fallback) instead of waiting on a timeout.
Why it matters
Retrying a down service multiplies load. A breaker protects your threads and gives the dependency room to heal.
How it is used
Half-open after a cooldown: allow a probe request through. If it works, close the breaker. Tune on real SLOs, not guesswork.