Comment by litewulf

[I am a Googler and my team works on part of this]

You can connect to postgres from app engine standard... as long as its Java. See this doc https://cloud.google.com/appengine/docs/standard/java/cloud-...

And no, appengine standard is not a second class citizen. Hand-wave-ily, the connectivity path that flex uses works for postgres with minimal changes, but unfortunately some additional work is required to get appengine standard for other languages working for postgres. :(