Async vs Sync http requests

tasks.exs

defmodule Tasks do
  def main(_args) do
    HTTPoison.start
    
    # data gov caches the requests so i had to spin up a json server,
    # which does not have caching to accurately test the async/sync time.
    urls = [
            "https://data.gov.uk/data/api/service/transport/planned_road_works/road?road=M62",
            "https://data.gov.uk/data/api/service/transport/planned_road_works/road?road=M62",
          ]

    {microsec, _} = :timer.tc fn ->
      urls
        |> Enum.map(fn(url) -> Task.async(fn -> HTTPoison.get(url,[],timeout: 1500) end) end)
        |> Enum.map(&Task.await(&1, 30000))
        |> Enum.each(fn({status, result}) ->
          if (status == :ok) do
            IO.inspect result.status_code
          else
            IO.inspect result.reason
          end
        end)
    end
    IO.puts "async took #{microsec} microsecs"

    {microsec, _} = :timer.tc fn ->
      urls
        |> Enum.map(fn(url) -> HTTPoison.get(url,[],timeout: 1500) end)
        |> Enum.each(fn({status, result}) ->
          if (status == :ok) do
            IO.inspect result.status_code
          else
            IO.inspect result.reason
          end
        end)
    end
    IO.puts "sync took #{microsec} microsecs"

  end
end

➜  tasks git:(master) ✗ mix escript.build && ./tasks
Compiled lib/tasks.ex
Generated escript tasks with MIX_ENV=dev
number of urls: 1
async took 0.403556 seconds
sync took 0.029024 seconds
➜  tasks git:(master) ✗ mix escript.build && ./tasks
Compiled lib/tasks.ex
Generated escript tasks with MIX_ENV=dev
number of urls: 4
async took 0.474734 seconds
sync took 0.072134 seconds
➜  tasks git:(master) ✗ mix escript.build && ./tasks
Compiled lib/tasks.ex
Generated escript tasks with MIX_ENV=dev
number of urls: 24
async took 1.43528 seconds
sync took 0.872841 seconds
➜  tasks git:(master) ✗ mix escript.build && ./tasks
Compiled lib/tasks.ex
Generated escript tasks with MIX_ENV=dev
number of urls: 96
async took 2.752861 seconds
sync took 3.302035 seconds
➜  tasks git:(master) ✗ mix escript.build && ./tasks
Compiled lib/tasks.ex
Generated escript tasks with MIX_ENV=dev
number of urls: 384
async took 9.253165 seconds
sync took 20.645522 seconds