Phoenix (Elixir) for the backend because I started with Elixir this year and really enjoy it. If the app was simple enough and I was feeling up for a challenge

Phoenix (Elixir) for the backend because I started with Elixir this year and really enjoy it. If the app was simple enough and I was feeling up for a challenge than maybe just Erlang directly with Cowboy (so no real framework). For the front end: Elm or maybe Ember.js. I started learning Elm this year too and like it but I possibly would go Ember because it seems interesting and since I have a membership to Daily Drip I have free tutorials on Ember (as well as Elm and Elixir)