gistfile1.rb

# make this class in lib/transactional_requests.rb, and load it on start
require 'activerecord'

class TransactionalRequests
  def initialize(app)
    @app = app
  end

  def call(env)
    ActiveRecord::Base.transaction do
      @app.call(env)
    end
  end
end

# and in the app config
config.middleware.use "TransactionalRequest"