http://highscalability.com/blog/2014/2/26/the-whatsapp-architecture-facebook-bought-for-19-billion.html

"Interesting to note Facebook Chat was written in Erlang in 2009, but they went away from it because it was hard to find qualified programmers."

Same year Brian Barton was turned down.

Interesting stats

450 million active users, and reached that number faster than any other company in history.

32 engineers, one developer supports 14 million active users

50 billion messages every day across seven platforms (inbound + outbound)

1+ million people sign up every day

$0 invested in advertising

$8 million investment

Hundreds of nodes

>8000 cores

Hundreds of terabytes of RAM

>70M Erlang messages per second

In 2011 WhatsApp achieved 1 million established tcp sessions on a single machine with memory and cpu to spare. In 2012 that was pushed to over 2 million tcp connections. In 2013 WhatsApp tweeted out: On Dec 31st we had a new record day: 7B msgs inbound, 11B msgs outbound = 18 billion total messages processed in one day! Happy 2013!!

./bernard