The benefit of iex.exs is being able to print helpful reminder messages in a production/staging/dev shell.

Example:

is_staging = !!System.get_env("IS_STAGING")

mix_env =
  case {System.get_env("MIX_ENV"), Application.get_env(:my_app, :env)} do
    {"prod", :prod} -> :prod
    {_, :test} -> :test
    {_, :dev} -> :dev
    _ -> :unknown
  end

print_warning = fn message ->
  IO.puts(IO.ANSI.red_background() <> message <> IO.ANSI.blink_rapid() <> IO.ANSI.reset())
end

print_info = fn message ->
  IO.puts(IO.ANSI.cyan_background() <> message <> IO.ANSI.reset())
end

print_warning_if_prod = fn ->
  case {mix_env, is_staging} do
    {:prod, false} ->
      for message <- ["⚠ REMINDER:", "👿 THIS IS THE PROD SHELL!", "🙇 PLEASE BE CAREFUL."] do
        print_warning.(message)
      end

    {:prod, true} ->
      print_warning.("👷 this is the staging shell")

    {_, _} ->
      print_info.("Welcome to MyApp, Dev 👽")
  end
end

print_warning_if_prod.()
print_info.(" 🌎 Your region: " <> System.get_env("FLY_REGION", "local-dev"))

With the above (or similar) in the iex.exs file, connecting to remote shells is safer. The developer is reminded of the environment.