---
apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingAdmissionPolicy
metadata:
  name: "enforce-multiple-replicas-deployments"
  annotations:
    kubernetes.io/description: "Require that matching Deployments have multiple replicas"
spec:
  matchConstraints:
    resourceRules:
    - apiGroups:   ["apps"]
      apiVersions: ["v1"]
      resources:   ["deployments"]      # the Deployment API
      operations:  ["CREATE", "UPDATE"] # the API verb, converted to upper case
  validations:
    - expression: "object.spec.replicas >= 2"