If you design your MVP with a REST layer in between written in Erlang/Elixir and use Mnesia for prototyping it could take you a long way and would be v. easy t

If you design your MVP with a REST layer in between written in Erlang/Elixir and use Mnesia for prototyping it could take you a long way and would be v. easy to scale. Mnesia has its limits as a NoSQL database so later you would probably switch to a RDBMS. For HTML-generation it will be better to write the code in Ruby or Python or whatever else.