API Observability: Monitoring Integration Health
API integrations fail in production — third-party APIs have outages, authentication tokens expire, rate limits are hit, response schemas change without notice. API observability provides the visibility needed to detect, diagnose, and resolve integration failures before they cause significant business impact.
What to Monitor
- Error rates: Percentage of API calls returning errors (4xx, 5xx responses). Alert when error rate exceeds a threshold.
- Latency: P50, P95, P99 response times from each integrated API. Degraded third-party performance often precedes complete outages.
- Availability: Track whether key integration endpoints are reachable. Synthetic monitoring sends test requests on a schedule.
- Rate limit consumption: Monitor rate limit headers — alert when approaching limits before they cause failures.
- Webhook delivery: Track webhook delivery success rates and retry queue depths.
Alerting Strategy
Alert on integration failures that affect user-facing functionality immediately. Alert on degraded performance (latency increases, rising error rates) with longer thresholds — these often precede complete failures. Suppress alerts during known maintenance windows.
Structured Logging for Integration Calls
Every external API call should be logged with: timestamp, target API and endpoint, request ID, response status, latency, and correlation ID linking it to the originating user request. Structured logs make debugging integration failures significantly faster.
Circuit Breakers
The circuit breaker pattern temporarily stops calling a failing API when error rates are high — preventing cascading failures in dependent systems. When the API recovers, the circuit closes and calls resume. Libraries like Hystrix and Resilience4j implement this pattern.