As an outsider, I would guess huge swaths of developers with a massive hierarchy. Buildings full of folks working on AWS services. I have no idea and extremely curious.
at least 12 people. Of course they are in turn supported by many different teams, which also consist of who knows how many people.
Then, as the scale increases, and the number of features increase, so do the number of teams.
Lambda and CloudWatch are both a couple hundred people which wouldn't be surprising once you consider all the things that they do.
But I would venture a good half of all AWS services are built and run by one team of 10-12.