They were two viral web apps that blew up on twitter. They had approx 25,000 users at their peak.

Originally they were built on Postgres, so we helped move over to us. Their graph had about 50,000 user nodes and 25 million edges (follower connections). This then made it a lot more optimised to handle the highly interconnected users to find shortest paths between one user and Elon Must / Donald Trump.

So to sum it up, they stored clones of all the users and how they were interconnected by follower relationships, and then used our query language to super easily calculate the shortest paths.