I don't know why you are being down-voted. Premateralized flat files pushed out to heavy-duty CDNs would get you very, very far. I would think that dealing with CSAM, death-threats, and other things that would get your platform into trouble would be the more difficult problem to manage. I could very easily see the technical parts of Twitter being run with a few hundred people. I don't know what else would be involved for legal, finance, marketing, sales, etc. But I doubt it is 8,000+ people.