The way Google deploys applications is fundamentally different than the model they expose to customers. Google's cloud platform runs on top of their real resource management system, not the other way around.
I worked there in 2011 and I'm pretty sure not everything was on AWS at that time.
I don't know how to square that with the tweet: my own understanding could be wrong, or it could be a misleading stat like 100% of public traffic hits a server on AWS infrastructure but not all of the other backend services were.
