I’m new to AWS deployment and facing an issue with my Elixir/Phoenix application.

I’ve deployed my app to AWS ECS, but I’m encountering a problem with environment variables.

All the configurations in prod.exs that fetch values from environment variables using System.get_env() are returning nil.

In my prod.exs file:

config :my_app, :my_variable, System.get_env("MY_VARIABLE")
...

And in my module:

defmodule MyApp.MyModule do
  @my_variable Application.compile_env(:my_app, :my_variable)

  def get_variable, do: Application.get_env(:my_app, :my_variable)
  ...
end

Both of these methods return nil.

However, strangely, System.get_env("DATABASE_URL") in runtime.exs works fine (the app won’t function without a database connection). This indicates that the app can read the environment variables defined in the Task Definition.

Now, I’m confused about how runtime and compile time handle environment variables. How can I resolve this issue in my case? Where should I place my configurations? When should I inject environment variables for compile time?

Should I move all the configurations to runtime.exs and stop using Application.compile_env/2 ?

Help me please.