What are default VPC firewall rules for App Engine Flex
I have a few services deployed in one App Engine flexible environment project. The service instances are running in the same VPC network (not default) which is specified in their app.yaml files and assigned IP addresses from the same subnetwork. By default both services are accessible from outside and I want to configure firewall rules to leave only the default service allowed for incoming traffic. So as the first step I'm configuring a rule to deny all ingress for all instances in this VPC, with the idea of creating another rule with a higher priority to allow traffic to only one instance