apiVersion: policies.kyverno.io/v1alpha1
kind: ValidatingPolicy
metadata:
  name: check-deployment-replicas
spec:
  matchConstraints:
    resourceRules:
    - apiGroups:   ["apps"]
      apiVersions: ["v1"]
      operations:  ["CREATE", "UPDATE"]
      resources:   ["deployments"]
  validations:
    - expression: "object.spec.replicas <= 2"
      message: "Deployment replicas must be less than or equal 2"