Node.js: A simple pattern to increase perceived performance

The asynchronous nature of code running on Node.js provides many interesting options for service orchestration. In this example I will call two translation services (Google and SYSTRAN). I will call both of them quickly after each other (milliseconds). The first answer to be returned, will be the answer returned to the caller. The second answer will be ignored. I've used a minimal set of Node modules for this; http, url, request. Also I wrapped the translation API's to provide a similar interface which allows me to call them with the same request objects. You can download the code here. In the below picture this simple scenario is illustrated. I'm not going to talk about the event loop and the call stack. Watch this presentation for a nice elaboration on those.