http://www.wired.com/2015/09/whatsapp-serves-900-million-users-50-engineers/ > Facebook built its original Facebook Chat app in Erlang but eventually rebuilt so that it would better fit with the rest of its infrastructure. “You had this little island that was Erlang, and it was hard to build enough boats back to the island to make everything hook in,” says Facebook vice president of engineering Jay Parikh.

that quote reminds me of one of the good things about Clojure — that it can bridge to an organization’s existing Java libraries/frameworks

Holy crap, 50 engineers!! That seems like a lot.

But consider the number of users to engineers as a ratio. Pretty insane. Personally, I think it’s kind of funny FB moved away from Erlang in their system, and then brought it in through the largest acquisition in history

(Though the reason FB moved away, as well as the reason WhatsApp uses Erlang both seem pretty reasonable)

Just 50 engineers for ~1B users is awesome.

Compared to e.g. Google