What you should do is have your Ecto schemas and GraphQL resolvers in the same package with the Ecto Repo, but don’t add it to your supervision tree. In order to do that you’ll have to configure the :otp_app part so your Ecto schema/GraphQL package’s repo. This would mean your non-main package would just define schemas, resolvers and a repo but wouldn’t start them or do anything (they’re just plain modules then). Be warned though, compilation will fail if you do not configure it! (i.e. in tests or other areas) This would look something like:

defmodule API.Repo do
  @otp_app Application.get_env(:api, :otp_app)
  use Ecto.Repo, otp_app: @otp_app, adapter: Ecto.Adapters.Postgres
  use Absinthe.Ecto, otp_app: @otp_app
end

Then in your main app do the following in config:

config :api, otp_app: :main_app

# Config for Ecto repos & database connection here
config :main_app, ecto_repos: [API.Repo]
config :main_app, API.Repo,
  # ...

Finally in your main app supervision tree:

def start(_type, _args) do
  children = [
    API.Repo,
  ]

  # ...
end

I managed to get around that using a FakeRepo lol.

defmodule Enderecify.FakeRepo do
  use Ecto.Repo,
    otp_app: :enderecify_api,
    adapter: Ecto.Adapters.Postgres
end