Interview Questions/Phone Screen/K8s Readiness vs Liveness Probes

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2 min

K8s Readiness vs Liveness Probes

Kubernetes Reliability Troubleshooting

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Interview Question

What is the difference between readiness and liveness probes in Kubernetes?

Key Points to Cover

Readiness gates traffic until pod is ready; failing removes from endpoints
Liveness restarts the container when it gets unhealthy
Probes: HTTP/TCP/exec with initialDelay, period, thresholds

Evaluation Rubric

Explains readiness behavior34% weight

Explains liveness restart semantics33% weight

Mentions probe types and tuning33% weight

Hints

💡A startup probe can protect slow apps from restarts.

Common Pitfalls to Avoid

⚠️**Misusing probes:** Using a liveness probe to check for application readiness, leading to continuous restarts when the application is merely warming up.
⚠️**Overly aggressive probe settings:** Setting `initialDelaySeconds` too low, or `periodSeconds` and `failureThreshold` too short, causing premature restarts or traffic removal for temporary issues.
⚠️**Probes not reflecting true application health:** Checking only basic HTTP status codes (e.g., 200 OK) when the application might be running but functionally broken (e.g., unable to connect to a critical backend service).
⚠️**Long-running Exec probes:** An `exec` command that takes too long to complete might exceed `timeoutSeconds` and be mistakenly considered a probe failure.
⚠️**Not using both probes:** Relying solely on liveness or readiness, missing out on the complementary benefits for robust fault tolerance, such as isolating non-ready pods while gracefully restarting truly unhealthy ones.

Potential Follow-up Questions

❓When to use startup probes?
❓Common pitfalls causing restart loops?

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