class AWS::DynamoDB::Client

def sleep_durations response
  retry_count = 
    if expired_credentials?(response)
      config.max_retries == 0 ? 0 : 1
    else
      config.max_retries { 10 }
    end
  # given a retry_count of 10, the sleep durations will look like:
  # 0, 50, 100, 200, 400, 800, 1600, 3200, 6400, 12800 (milliseconds)
  (0...retry_count).map do |n|
    if n == 0
      0
    else
      50 * (2 ** (n - 1)) / 1000.0
    end
  end
end