Earlier quoted context omitted.
thats a naive assumption, there could be a lot of hidden scaling issues when you think deeper about how it works
I don't doubt it's challenging to keep the thing up, but 4100 employees? And meanwhile WhatsApp has 50 or so employees in total.
This isn't a knock on WhatsApp -- I use WhatsApp and don't use Twitter -- but Twitter's scale challenges are vastly more complex than WhatsApp's, which doesn't have many features that can't just very simply horizontally scale.