When you deploy your app on App Engine with

gcloud app deploy

, the platform runs it in a container along with a side-car container in charge of running the cloud_sql_proxy (you ask for it by specifying the

base_settings:cloud_sql_instances

in your app.yaml file).

Kubernetes Engine doesn't use an app.yaml file and doesn't supply this side-car container to you so you'll have to set it up. The public doc shows how to do it by creating secrets for your database credentials and updating your deployment file with the side-car container config. An example shown in the doc would look like:

...
- name: cloudsql-proxy

  image: gcr.io/cloudsql-docker/gce-proxy:1.11

  command: ["/cloud_sql_proxy",
            "-instances=<INSTANCE_CONNECTION_NAME>=tcp:3306",
            "-credential_file=/secrets/cloudsql/credentials.json"]

  securityContext:

    runAsUser: 2  # non-root user

    allowPrivilegeEscalation: false

  volumeMounts:
    - name: cloudsql-instance-credentials

      mountPath: /secrets/cloudsql

      readOnly: true
...