ReplicaSets and Deployments

You run kubectl set image to push a new container version, and three minutes later the rollout is stuck: new Pods crash-looping, old Pods draining, kubectl rollout status hanging at "1 out of 3 new replicas have been updated." Understanding the machinery underneath (how ReplicaSets maintain Pod count and how Deployments orchestrate replacements) is what separates a quick rollout undo from a panicked troubleshooting session.

ReplicaSets and Deployments span two CKAD exam domains. Application Design and Build (20%) tests whether you can "choose and use the right workload resource." Application Deployment (20%) asks you to "understand Deployments and how to perform rolling updates." You will create Deployments imperatively, scale them, update images, roll back to specific revisions, and inspect rollout history under time pressure.