How to configure communication between standard env app-engine & cloudsql instance with internal ip

Question

I configure a serverless vpc,& launch the app with following app.yaml. But unable to communicate the private sql instance.

runtime: python37
service: xxxx
entrypoint: gunicorn main:app --bind 0.0.0.0:$PORT --worker-class sanic.worker.GunicornWorker

vpc_access_connector:
  name: "projects/xxxx/locations/us-central1/connectors/serverless-vpc-name"

inbound_services:
- warmup

env_variables:
  PROJ_NAME: xxxxx
  DB_TYPE: mysql_socket
  SQL_USERNAME: root
  SQL_PASSWORD: xxxxx
  SQL_DATABASE_NAME: xxxxx
  SQL_CONNECTION_NAME: xxxx:us-central1:cloudsql-instance```

Answer 1

According to official documentation link:

If you are connecting from App Engine, you must use flexible environment. You cannot use private IP to connect from standard environment.

Here you can find more documentation Connecting to Cloud SQL from App Engine

However you can use Serverless VPC Access to connect from your App Engine app directly to Cloud SQL instances, and any other resources with an internal IP address.

Connecting to a VPC network