So I heard a bit differently about the FB Chat thing. Facebook likes to move its engineers around to different teams from time to time (if only temporarily) to

So I heard a bit differently about the FB Chat thing. Facebook likes to move its engineers around to different teams from time to time (if only temporarily) to spread institutional knowledge around and prevent bus factors from being too low. This also is a way to alleviate burnout. There simply weren't enough engineers at FB who knew Erlang to make this practical for chat, so they rewrote it in C++. The Erlang bits were reasonably written and working fine, but it didn't fit into this policy. Any non-mainstream languages wouldn't fit, this isn't something about Erlang in particular. Erlang is a great fit for a number of problem domains, but if you silo it into a small part of your organization, you're going to run into issues such as these. You have to be willing to train people in it. It isn't that hard to pick up if it's someone's full time job to do so, as long as they're smart. And you want to hire smart people anyway, right?