Extending the deployments with network policies

A Network Policy can regulate what can talk to what.

Simply put, if you don't want your database to talk to anything other than a specific service, you can use a network policy like this:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: db-network-policy
  namespace: default
spec:
  podSelector:
    matchLabels:
      app: db
  policyTypes:
  - Ingress
  - Egress
  ingress:
  - from:
    - podSelector:
        matchLabels:
          app: my-app
    ports:
    - protocol: TCP
      port: 5432
  egress:
  - to:
    - podSelector:
        matchLabels:
          app: my-app
    ports:
    - protocol: TCP
      port: 5432

to restrict traffict to the database.

important

A NetworkPolicy without a Network plugin in the cluster will not do anything.

A networking plugin is a CNI like calico.

Kind has its own CNI implementation using kindnet.