Comparison between sync/async solutions for simple web api

config.ru

# to be used with the sync version
require './request_handler_sync'
run Sinatra::Application

request_handler_async.rb

# completely async version built with
# https://github.com/igrigorik/em-synchrony
# and
# https://github.com/postrank-labs/goliath
require 'goliath'
require 'em-synchrony'
require "em-synchrony/em-redis"

class FbRequest

  HOST = "127.0.0.1"

  class << self

    def connection
      @connection ||= begin
         EventMachine::Synchrony::ConnectionPool.new(size: 2) do
           EM::Protocols::Redis.connect(:host => HOST)
         end
      end
    end

    def create!
      new.save
    end

  end

  def initialize
    @recipient  = 'foo'
    @sender = 'bar'
  end

  def save
    next_id = connection.incr('counter').to_s
    10.times do |n|
      connection.sadd(@sender + next_id, @recipient + n.to_s)
    end
    connection.expire(@sender + next_id, 120)
    connection.smembers(@sender + next_id)
  end

  def connection
    self.class.connection
  end

end

class RequestHandlerAsync < Goliath::API

  def response(env)
    req = FbRequest.create!
    [200, {"Content-Type" => "text/html"}, req.inspect]
  end

end

request_handler_sync.rb

# sync version using sinatra
require 'sinatra'
require 'redis'

class FbRequest

  HOST = '127.0.0.1'

  class << self

    def connection
      @connection ||= Redis.new(:host => HOST)
    end

    def create!
      new.save
    end

  end

  def initialize
    @recipient  = 'foo'
    @sender = 'bar'
  end

  def save
    next_id = connection.incr('counter').to_s
    10.times do |n|
      connection.sadd(@sender + next_id, @recipient + n.to_s)
    end
    connection.expire(@sender + next_id, 300)
    connection.smembers(@sender + next_id)
  end

  def connection
    self.class.connection
  end

end

get "/requests/new" do
  FbRequest.create!
end