Asobi is an Erlang/OTP game backend you can self-host. You write your match logic in Lua.

I wanted to build a game backend on Erlang/OTP. The BEAM is built for what multiplayer games actually do: lots of small concurrent processes, supervision, soft real-time, hot code loading. So I did. Matchmaker, leaderboards, voting, a world server, IAP, economy, friends, and chat are all in.