Refactors Before Features; 50 People Run Twitter

A legacy code base like Twitter's needs refactors before features: you first build trusted tests/CI before touching code, then replace old modules with simpler ones (e.g. 100k lines replaceable by 300 lines of Go), and Hotz believes 50 people could comfortably build and maintain Twitter — the code base grew because engineers get promoted for adding libraries others use, not for simplicity.