I don't remember that it was harder actually. We were using Mochiweb (was replaced by Cowboy at some point in time), Chicago Boss and some other additional Erla

I don't remember that it was harder actually. We were using Mochiweb (was replaced by Cowboy at some point in time), Chicago Boss and some other additional Erlang libs and people switched from it to Elixir and other way around. Agree with rossj, there're some rules to remember and then it's not that hard.