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hardDevOps Engineer interview question

How do you plan and carry out a Kubernetes version upgrade for production clusters with minimal risk?

What the interviewer wants to hear

  • Read release notes; find deprecated and removed APIs
  • Upgrade one minor version at a time; control plane before nodes
  • Test in lower environments first; check add-on compatibility
  • PodDisruptionBudgets and surge node pools for safe draining
  • Rollback plan, such as blue-green clusters, and monitoring

Model answer

I start with the release notes and scan all manifests and Helm charts for deprecated or removed APIs using tools like Pluto or kubent, then fix them before upgrading. I check that add-ons such as the CNI, ingress controller, CSI drivers, service mesh and operators support the new version. Kubernetes supports upgrading one minor version at a time and has version skew rules, so the control plane goes first, then node pools. I upgrade dev and staging first and run tests. For nodes, I create a new node pool on the new version, cordon and drain old nodes gradually, and rely on PodDisruptionBudgets, multiple replicas and good readiness probes so services stay available. I watch error rates and cluster health during the process. For very critical systems, I prefer a blue-green cluster approach, moving traffic to a new cluster so rollback is simple.

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