I think Joel is a bit extremist here. IIRC EBay rewrote their backend three times. It was not because the previous version was wrong, but because they were gro

I think Joel is a bit extremist here. IIRC EBay rewrote their backend three times. It was not because the previous version was wrong, but because they were growing and changing, so a new backend was needed anyway to tackle that. They were and are doing fine. Twitter rewrote their codebase from Ruby on Rails (the endless source of fail whales) to a completely different platform, again due to the huge growth. Technology-wise, they are doing pretty fine. Facebook rewrote Messenger from a very thick and complex client architecture to an outrageously lightweight and flexible architecture based on eventual consistency / roughly-CRDT approach. FB Messenger is doing very fine. Never rewrite your codebase without a really good reason. Big wins in performance, maintainability, and ease of development may be good reasons, depending on your situation.