How to use MongoDb with Phoenix and Ecto. The latest versions of Ecto don’t support MongoDb. What to do? Don’t downgrade Ecto - You can use the latest version of Phoenix and Ecto directly with Elixir MongoDb Drivers with a small amount of code. Strategies and sample code for common tasks.

https://tomjoro.github.io/2017-02-09-ecto3-mongodb-phoenix/