I want to preface this with: I love erlang. We use Elixir for the service that powers metrics display for Wallaroo. When I learned Erlang several years ago, it made me a better programmer.

At the time we made the decision, we were worried about Erlang being able to meet the latency and throughput goals we had. I knew a number of people who worked on Riak at Basho and had a few lengthy discussions about Erlang performance. They felt that we could end up struggling to get the performance we were looking for.

I had never used Erlang for any large scale project and deferred to their wisdom and knowledge.

As it turns out, the approach that we've used to support languages like Python is in process, using C to bind Wallaroo with the other language. This probably would have been more difficult with Erlang as well, but that's hindsight.

Erlang is an awesome language. It has an amazing VM. That we didn't think it was right for us should in no way discourage anyone else from using it.

Just so you know, some of the earliest videos you can find about Pony are at Erlang conferences, probably because it is cited as a big influence (actor language). The two communities seem to be getting along very well.