Custom Resources: What Happens After Defining the Schema

Mon, 31 Aug 2026 00:00:00 +0000

This is part 2 of a four-part series on building a Kubernetes operator: CRDs , Custom Resources (this post), Operators and Kubebuilder .

More Than YAML That Passes Validation

Last time, I defined BackupCheck as a Custom Resource Definition (CRD) and applied a Custom Resource against it:

1apiVersion: backups.example.io/v1alpha1
2kind: BackupCheck
3metadata:
4  name: nightly-verification
5  namespace: data-platform
6spec:
7  targetCluster: postgres-prod
8  schedule: "0 3 * * *"
9  retentionDays: 14

In that last post, I created a CRD focussed on the schema, describing what shape the object, the resulting Custom Resource (CR), is supposed to take. What I have not mentioned is everything that happens to the object after it is created: how the API server tracks changes to it, how a controller safely coordinates concurrent writes, how deletion actually works, and how child objects it creates get cleaned up automatically. This is going to be functionally more interesting.

Custom-Resources on Felix Seifert

Custom Resources: What Happens After Defining the Schema

More Than YAML That Passes Validation