Health Checks

Different checks serve different purposes. Don't conflate them.

Check Types

Endpoint	Purpose	On Failure	Should Check
/health/live	Process alive?	K8s restarts pod	Only process responsiveness
/health/ready	Can handle traffic?	K8s removes from LB	DB, cache, critical deps
/health/startup	Init complete?	K8s waits	Initialization status

Liveness (Simple)

Return 200 OK immediately. Never check dependencies.

Checking DB in liveness = pod restarts when DB is down = cascading failure.

Readiness (Dependency Checks)

For each dependency:
  → Check with timeout (1-2s)
  → Record healthy/unhealthy status
Return 503 if any critical dependency unhealthy

Response Format

{
  "status": "healthy|unhealthy",
  "version": "1.2.3",
  "dependencies": {
    "database": "healthy",
    "cache": "unhealthy: connection refused"
  }
}

Kubernetes Config

livenessProbe:
  httpGet: { path: /health/live, port: 8080 }
  periodSeconds: 10
  failureThreshold: 3

readinessProbe:
  httpGet: { path: /health/ready, port: 8080 }
  periodSeconds: 5
  failureThreshold: 3

startupProbe:
  httpGet: { path: /health/startup, port: 8080 }
  periodSeconds: 5
  failureThreshold: 30  # 150s max startup

Anti-Patterns

• Liveness checks dependencies → Cascading restarts
• No timeout on checks → Health endpoint hangs
• No caching → Thundering herd on health endpoints

References

• references/platforms/{platform}/health-checks.md