[pankajdoharey]

Why did they not write the backend server for Whatsapp web in Erlang, which the original Whatsapp was mostly written in?

[sigalor]

Well, I don't know Erlang (yet) and AFAIK, Erlang is rather focused on fail tolerance, high availability etc., which wasn't really a concern when I started the project. Python and NodeJS are quite good for quickly trying out ideas though.