Performance is closely tied to resilience: how systems behave when dependencies are slow, failing or overloaded. Patterns like timeouts, retries and circuit breakers aim to contain failures and protect overall responsiveness.
Testing Timeouts, Retries and Circuit Breakers
Timeouts prevent calls from hanging indefinitely, retries handle transient failures and circuit breakers stop repeated calls to unhealthy dependencies. Performance tests should simulate partial failures to verify that these mechanisms trigger correctly and do not create thundering-herd or retry storms.
Resilience testing ideas:
- Inject latency or failures into a downstream service
- Verify that callers respect timeouts and degrade gracefully
- Observe circuit breaker state changes under sustained errors
- Check that retry policies back off instead of hammering dependenciesResilience-aware performance testing ensures that your system fails fast and recovers gracefully rather than timing out everywhere under stress.
Common Mistakes
Mistake 1 — Assuming dependencies will always behave well
This is unrealistic.
❌ Wrong: Designing tests where all downstream services are always fast and healthy.
✅ Correct: Include scenarios with partial failures and slowdowns.
Mistake 2 — Setting timeouts and retries without testing them
This hides configuration bugs.
❌ Wrong: Copy-pasting default settings without validation.
✅ Correct: Verify that policies behave as intended under load and failure.