Core settings
- Sliding window (count/time), failure rate threshold, slow-call threshold, minimum calls.
- Wait duration in open state; half-open permitted calls; automatic transition.
Patterns
- Wrap HTTP/DB/queue clients; combine with timeouts/retries/bulkheads.
- Tune per dependency; differentiate fast-fail vs. tolerant paths.
- Provide fallback only when safe/idempotent.
Observability
- Export metrics: state changes, calls/success/failure/slow, not permitted count.
- Log state transitions; add exemplars linking to traces.
- Alert on frequent open/half-open oscillation.
Checklist
- Per-downstream breaker with tailored thresholds.
- Timeouts and retries composed correctly (timeout → breaker → retry).
- Metrics/logs/traces wired; alerts on open rate.