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Node.js is a platform for building fast and scalable network applications — that’s pretty much what the Node.js website says. But Node.js is more than that: It’s the hottest JavaScript runtime environment around right now, used by a ton of applications and libraries — even browser libraries are now running on Node.js.

More importantly, this fast server-side execution allows developers to focus on more complex problems, such as Natural for natural language processing. Even if you don’t plan to write your main server application with Node.js, you can use tools built on top of Node.js to improve your development process; for example, Bower for front-end package management, Mocha for unit testing, Grunt for automated build tasks and even Brackets for full-text code editing.

So, if you’re going to write JavaScript applications for the server or the client, you should become familiar with Node.js, because you will need it daily. Some interesting alternatives exist, but none have even 10% of Node.js’ community.

MongoDB is a NoSQL document-based database that uses JavaScript as its query language (but is not written in JavaScript), thus completing our end-to-end JavaScript platform. But that’s not even the main reason to choose this database.

MongoDB is schema-less, enabling you to persist objects in a flexible way and, thus, adapt quickly to changes in requirements. Plus, it’s highly scalable and based on map-reduce, making it suitable for big data applications. MongoDB is so flexible that it can be used as a schema-less document database, a relational data store (although it lacks transactions, which can only be emulated) and even as a key-value store for caching responses, like Memcached and Redis.

Server-side componentization is never easy. But with Express (and Connect) came the idea of “middleware.” In my opinion, middleware is the best way to define components on the server. If you want to compare it to a known pattern, it’s pretty close to pipes and filters.

The basic idea is that your component is part of a pipeline. The pipeline processes a request (i.e. the input) and generates a response (i.e. the output), but your component isn’t responsible for the entire response. Instead, it modifies only what it needs to and then delegates to the next piece in the pipeline. When the last piece of the pipeline finishes processing, the response is sent back to the client.