I think for simple API endpoint Plug is still the best option

A simple example

    defmodule AddressParser.PlugHandler do
      import Plug.Conn
      require Logger

      def init(options) do
        Logger.info("Running #{__MODULE__} with Plug using http://0.0.0.0:8080")
        options
      end

      def call(
            %Plug.Conn{method: method, request_path: request_path, query_string: query_string} = conn,
            _opts
          ) do
        request_id = generate_request_id()
        Logger.info("#{request_id} #{method} #{request_path} #{query_string}")

        case handle_request(method, request_path, URI.decode_query(query_string)) do
          {:ok, response} ->
            Logger.info("#{request_id} sent 200 ok")

            conn
            |> put_resp_content_type("application/json")
            |> send_resp(200, Jason.encode!(response))

          {:error, status, response} ->
            Logger.error("#{request_id} sent #{status} #{response}")

            conn
            |> put_resp_content_type("text/html")
            |> send_resp(status, response)
        end
      end

      defp handle_request("GET", "/parse", %{"address" => address}) do
        {:ok, Address.parse(address)}
      end

      # more handlers
      ...
    end