Also, I have to say that elixir developers are generally not very experienced with it and seem to be generally less desirable than the people who are working with scala. You get rubyists that have some interest in working with elixir because there were some blog posts saying it's the new hotness. Scala seems to attract more comp-sci savvy people. And generally those people will refuse to work with elixir when there are Scala job out there that will pay. Startups should use scala for these reasons. Elixir may be a mistake for the resource pool alone.

One thing that's trecherous is that rubyists can bring whatever they believe to be the right way to do things and assume everything should be exactly the same, especially with regards to ecto vs active record. Elixir isn't ruby. Ecto isn't rails active record. Not anywhere close. It just happens to look like ruby and there are some influences in the design but Ecto tells you not too implement STI like rails does for example so don't assume you're going to do it like you would in rails. I'd argue ruby is more like scala than it is like elixir as it has multiple paradigms. Elixir is squarely functional, just a very very simple functional language. The skill ceiling is pretty low and it should take very little time for someone to get up to speed which is important because you won't find a big pool of rockstars using it in the job market so you'll have to hire good people without experience and hope they will be okay using elixir and not jump ship to go work with strong typed languages.