Hey @Fake51, here’s what I do.

Here is my health controller:

defmodule Sensetra.Web.HealthController do
  use Phoenix.Controller, log: false

  def alive(conn, _params) do
    json(conn, %{alive: true})
  end

  def ready(conn, _params) do
    if Application.get_env(:sensetra, :ready) do
      json(conn, %{ready: true})
    else
      send_resp(conn, 503, "")
    end
  end
end

Notice how the alive endpoint always returns true, but the ready endpoint is conditional on an application environment setting. In my config, that value defaults to false. Then, I just have a tiny genserver as the very last entry in my supervision tree that sets the value to true. This ensures that the application doesn’t indicate that it is ready until the entire supervision tree has booted.