Pods and ports

General Discussions
2

From your stack overflow post: you only “told” Kubernetes at what port something is listening inside the container, you didn’t specify to which port you’d like to map that.

I personally, would put a service in front of it as documented here:
https://kubernetes.io/docs/concepts/services-networking/service/

kind: Service
apiVersion: v1
metadata:
name: my-postgres-service
spec:
  selector:
    app: my-postgres-app
  ports:
  - protocol: TCP
    port: 80 #That's the port you'll use to connect
    targetPort: 55432 # that's the port at which your app (your postgres) is listening