Payment (revenue) and inventory (order fulfillment) are critical. A payment failure means lost revenue; inventory failure means overselling. Other services can use cached/default values.

If the circuit trips during normal operation, the threshold is probably too sensitive. Normal network jitter or occasional slow responses are triggering it. Raise the threshold.

The reset timeout determines how long the circuit stays open before testing recovery. If it's too long, users experience unnecessary degradation after the service has recovered.

A failure in Half-Open means the service isn't fully recovered yet. The circuit should reopen immediately to prevent further failed requests and give more recovery time.

During an outage, the fallback is called for every request. If your fallback does heavy computation (instead of returning cached data), CPU spikes. Fallbacks should be lightweight.

An optimistic fallback that always says 'in stock' can lead to overselling. You'll accept orders you can't fulfill, causing customer frustration and operational headaches.

Each service should protect itself from its dependencies. B needs a circuit breaker for C. A needs one for B. This prevents C's failure from cascading through B to A.

This is 'flapping' or 'thrashing'. It happens when the service is partially healthy - just good enough to pass Half-Open tests but not stable enough to stay closed. Consider requiring multiple successful Half-Open requests.

The failure rate is 5/10 = 50%, which equals the threshold. At 50% threshold, this should trip the circuit. Note: some implementations use > vs >=, so this could be borderline.

Rate limit responses (429 Too Many Requests) are being counted as failures. You should configure the circuit breaker to NOT count 429s as failures, or implement pre-circuit rate limiting.