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-

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-2011/ https://blog.whatsapp.com/index.php/2012/01/1-million-is-so-... http://blog.whatsapp.com/index.php/2011/09/one-million/‎ http://blog.whatsapp.com/index.php/2011/09/one-million/‎ http://www.erlang-factory.com/upload/presentations/558/efsf2012-whatsapp-scaling.pdf http://www.erlang-factory.com/upload/presentations/558/efsf2... Perhaps those would make a good starting point?