Interview › Kubernetes, Docker, Helm & Podman
What is the difference between a liveness, readiness, and startup probe?
Kubernetes, Docker, Helm & Podman · Basic level
Answer
A liveness probe answers whether the container should be restarted, a readiness probe answers whether it should receive traffic, and a startup probe gives slow-starting applications time to become healthy before liveness begins.
Technical explanation
Startup probes disable liveness and readiness checks until startup succeeds, which prevents premature restarts for slow applications.
Probe thresholds, timeoutSeconds, and periodSeconds must reflect real app behavior, not arbitrary defaults.
Health and resources are production controls, not just YAML fields; wrong settings cause outages, noisy restarts, bad rollouts, or wasted capacity.
Requests affect scheduling and node capacity planning; readiness affects traffic; liveness affects restart behavior.
Validate settings with real load, startup timing, memory profiles, and deployment rollout behavior.
Hands-on example
1. Create a namespace and deploy a small HTTP app specifically to test: add liveness, readiness, and startup probes to a slow-starting app.
2. Add probes and resources in YAML, then run kubectl describe pod, kubectl top pod, and kubectl rollout status to observe behavior.
3. Introduce a controlled failure such as slow startup, bad health endpoint, CPU load, or memory spike.
4. Tune thresholds, requests, and limits until rollout and runtime behavior are stable, then document the production values and why.
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