The first three results on google for me for 'whatsapp freebsd erlang concurrent connection' are -

https://blog.whatsapp.com/index.php/2012/01/1-million-is-so-...

http://blog.whatsapp.com/index.php/2011/09/one-million/‎

http://www.erlang-factory.com/upload/presentations/558/efsf2...

Perhaps those would make a good starting point?

Whatapp old video talk and presentation on it. You can search it on HN.

Um... it's not easy to get 2-3million they did it but they also profile the crap out of it.

I think they easily got 1 million out of the box though.

Can I get anything like this with a more common tech stack? I.e. Node JS, Java + NIO, Python + Twisted (or something else)? 10K, I get. But 1 million+ is freakin awesome in my books.