CRDs, Operators, and Custom Controllers

Every time you run kubectl get certificate or kubectl get prometheusrule, you're hitting the Kubernetes API against a resource type that Kubernetes didn't ship with. CRDs made that endpoint exist. Operators made it useful.

The CKA exam includes "Understand CRDs, install and configure operators" in the Cluster Architecture domain, which carries 25% of your exam score. The competency is explicitly operational: the exam won't ask you to write a Go controller or scaffold a project with kubebuilder. It will test whether you can install an operator from its manifests, create a custom resource, and understand what happens to the cluster when you do.