We have Elixir/Phoenix in production on Heroku (with Heroku Pipelines) using a custom buildpack [0]. It's been great. We'll probably look at Docker. We use CircleCI, and this setup script [1] was a great starting point.

0: https://github.com/HashNuke/heroku-buildpack-elixir 1: https://gist.github.com/joakimk/48ed80f1a7adb5f5ea27