CRDs and the Operator pattern

WHAT IT TESTS: whether you understand how Kubernetes is extended using its own primitives. ANSWER OUTLINE: a CRD registers a new custom resource type with the apiserver, so you can create objects of your own kind that are stored and served like native ones, but a CRD alone is inert data. An Operator pairs that CRD with a custom controller that watches those resources and runs a reconciliation loop, encoding human operational knowledge to manage complex stateful apps like databases.