Kubernetes Advanced

Advanced Kubernetes covers Custom Resource Definitions (CRDs), Operators (reconcile loop), admission webhooks (validating/mutating), Pod Security Standards, topology spread, and multi-cluster with Cluster API or fleet management.

# Custom Resource Definition
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  name: paymentgateways.payments.example.com
spec:
  group: payments.example.com
  versions:
    - name: v1
      served: true
      storage: true
      schema:
        openAPIV3Schema:
          type: object
          properties:
            spec:
              type: object
              properties:
                replicas: { type: integer }
                acquirerEndpoint: { type: string }

# Operator reconcile loop (Java — Fabric8)
public void reconcile(PaymentGateway resource) {
  Deployment dep = buildDeployment(resource);
  client.apps().deployments().inNamespace(ns).createOrReplace(dep);
}