Often something like this would come from the application config.

Out of the box, the “prod.exs” file generated in a new Phoenix project would look for a file called prod.secret.exs with the idea that you would put that secret file in place while you build the release (i.e. not checked in source control). You can get at that config information using Application.get_env()

The static config files may or may not work for you depending on how your release is built though.

In practice I’ve found that it is more convenient for us to pass this kind of configuration information into the production environment as an environment variable and use System.get_env() to get at it. This may be because of our build pipeline, however, which makes the environment variable thing “easy” while a prod.secret.exs file would have to be generated, and the app recompiled, for our separate staging, RC, and prod environments.