Schrödinger's Service: Why Your Microservice Is Both Up and Down Until You Observe It

Short summary

Health checks collapse a service's true state into a single observation that often doesn't reflect what users experience. A service can return 200 on /health while failing on cold code paths, writing to a broken primary, or serving subtly wrong data. The fix is accepting that service health is multi-dimensional and requires independent probes: liveness, readiness, saturation, correctness, and real user-facing signals.

• •Health checks measure one dimension but users experience many
• •Three real patterns: warm path fine/cold path broken, replica fine/primary not, process alive/logic wrong
• •Need multiple independent observations: liveness, readiness, saturation, correctness, user signals

Generated with AI, which can make mistakes.