1 Answers
Hello! As you alluded to in your question, App Engine Flexible does support VPC access, so you should be able to connect through that to your own interconnected data centre (via Cloud VPN or what have you, and BGP/routing handled by the Cloud Router).
App Engine Standard has not historically supported VPC access like this, but Google is currently beta-testing a feature that does let you do this (i.e. connect to VPCs) with App Engine Standard, too!