Managed Kubernetes makes the control-plane upgrade a button. The button does not tell you what will break in the workloads, and it does not tell you that the node-pool roll will stall at the first node with a bad PodDisruptionBudget. This is the checklist to run on a cluster (call it prod-eu-1) before you press it. The first four sections apply everywhere; the last covers what differs on AKS, EKS and GKE.

0. Read the release notes and pick a target

Upgrade one minor version at a time. Kubernetes does not support skipping minors on the control plane, and the managed providers enforce this in different ways. Read the upstream changelog for the target version, specifically the "Urgent upgrade notes" and "Deprecation" sections, and your provider's own release notes for that version.

1. APIs removed in the target version

Kubernetes removes beta API versions on a published schedule. The authoritative list is the upstream deprecated API migration guide at kubernetes.io.…