In my mind the issue is less “is it conceivable that a small team can run a bare bones version of the Twitter app with hundreds of millions of users” and more “

In my mind the issue is less “is it conceivable that a small team can run a bare bones version of the Twitter app with hundreds of millions of users” and more “can a small team manage a big distributed system that was designed to be managed by many different teams, with no handoff period”.