10 Tips to Make Your Node.js Web App Faster

August 25, 2014

Node.js is already blazing fast thanks to its event driven and asynchronous nature. But, in the modern web just being fast is not enough. If you are planning to develop your next web app using Node.js you must take every possible step to make sure your app is faster than usual. This article presents 10 tips that are known to speed up your Node based web app tremendously. So, let’s see each of them one by one.

1. Run in Parallel

While building web apps, sometimes you will need to make multiple internal API calls to fetch various data. For instance, think about a user dashboard. While rendering the dashboard you may execute the following hypothetical calls:

The user profile – getUserProfile().
The recent activity – getRecentActivity().
Subscriptions – getSubscriptions().
Notifications – getNotifications().

In order to retrieve these details you might create a separate middleware for each function and attach to the dashboard route. But the problem with this approach is that one function has to wait for the previous one to complete. The alternative option is to execute these calls in parallel.

As we all know Node.js is very efficient in running multiple functions in parallel due to its asynchronous nature. We should take advantage of this. As the functions I mentioned above don’t depend on each other we can run them in parallel. This will cut down the number of middlewares and improve the speed greatly.

To parallelize things we can use async.js, a Node module that helps tame asynchronous JavaScript. Here is a snippet that shows how different functions may run in parallel using async.js:

function runInParallel() {
  async.parallel([
    getUserProfile,
    getRecentActivity,
    getSubscriptions,
    getNotifications
  ], function(err, results) {
    //This callback runs when all the functions complete
  });
}

If you want to learn more about async.js be sure to check out the project’s GitHub page.

2. Go Asynchronous

By design Node.js is single threaded. Because of this fact, synchronous code can potentially lock up the entire application. For example, most of the file system APIs have their synchronous counterparts. The following snippet shows how a file read operation can be done both synchronously and asynchronously:

// Asynchronous
fs.readFile('file.txt', function(err, buffer) {
  var content = buffer.toString();
});

// Synchronous
var content = fs.readFileSync('file.txt').toString();

But if you perform long running and blocking operations, your main thread will be blocked until the operation finishes. This dramatically reduces the performance of your app. So, make sure you always use asynchronous APIs in your code, at least in performance critical sections. Also be careful while choosing third party modules. Even if you take every precaution to avoid synchronous code, an external library could make a synchronous call, affecting your app’s performance.

3. Use Caching

If you are fetching some data that doesn’t change frequently, you may cache it to improve performance. For example, take the following snippet which fetches the latest posts to display on a view:

var router = express.Router();

router.route('/latestPosts').get(function(req, res) {
  Post.getLatest(function(err, posts) {
    if (err) {
      throw err;
    }

    res.render('posts', { posts: posts });
  });
});

If you don’t publish blog posts too frequently, you can cache the posts array and clear the cache after an interval. For example, we can use the redis module to achieve this. For that you need to have Redis installed on your server. Then you can use a client called node_redis to store key/value pairs. The following snippet shows how we can cache the posts:

var redis = require('redis'),
    client = redis.createClient(null, null, { detect_buffers: true }),
    router = express.Router();

router.route('/latestPosts').get(function(req,res){
  client.get('posts', function (err, posts) {
    if (posts) {
      return res.render('posts', { posts: JSON.parse(posts) });
    }

    Post.getLatest(function(err, posts) {
      if (err) {
        throw err;
      }

      client.set('posts', JSON.stringify(posts));    
      res.render('posts', { posts: posts });
    });
  });
});

So, first we check if the posts exist in the Redis cache. If so, we deliver the posts array from cache. Otherwise, we retrieve the content from the DB and then cache it. Also, after an interval we can clear the Redis cache so that new content can be fetched.

4. Use gzip Compression

Turning on gzip compression can hugely impact the performance of your webapp. When a gzip compatible browser requests for some resource, the server can compress the response before sending it to the browser. If you don’t use gzip for compressing your static resource it might take longer for the browser to fetch it.

In an Express app, you can use the built in express.static() middleware to serve static content. Additionally, you can use the compression middleware to compress and serve the static content. Here, is a snippet that shows how to do it:

var compression = require('compression');

app.use(compression()); //use compression 
app.use(express.static(path.join(__dirname, 'public')));

5. Use Client Side Rendering When Possible

With the emergence of many powerful client side MVC/MVVM frameworks like AngularJS, Ember, Meteor, etc., it has become very easy to create single page apps. Basically, instead of rendering on the server side you will just expose APIs that send JSON responses to the client. On the client side you can use a framework to consume the JSON and display on the UI. Sending JSON from the server can save bandwidth and thus improve speed because you don’t send layout markup with each request. Rather you just send plain JSON which is then rendered on the client side.

Take a look at this tutorial of mine which describes how to expose RESTful APIs with Express 4. I also wrote another tutorial which shows how to interact with these APIs using AngularJS.

6. Don’t Store Too Much in Sessions

In a typical Express web app, the session data is by default stored in memory. When you store too much data in the session, it adds significant overhead to the server. So, either you can switch to some other type of storage to keep session data or try to minimize amount of data stored in session.

For example, when users log into your app you can just store their id in the session instead of storing the entire object. Subsequently, on each request you can retrieve the object from the id. You may also want to use MongoDB or Redis to store session data.

7. Optimize Your Queries

Suppose you have a blogging app which displays the latest posts on the home page. You might write something like this to fetch data using Mongoose:

Post.find().limit(10).exec(function(err, posts) {
  //send posts to client
});

But the problem is that the find() function in Mongoose fetches all the fields of an object and there might be several fields in the Post object which are not required on the homepage. For instance, comments is one such field which holds an array of comments for a particular post. As we are not showing the comments we may exclude it while fetching. This will definitely improve the speed. We can optimize the above query with something like this:

Post.find().limit(10).exclude('comments').exec(function(err, posts) {
  //send posts to client
});

8. Use Standard V8 Functions

Different operations on collections such as map, reduce, and forEach are not supported by all browsers. To overcome the browser compatibility issues we have been using some client side libraries on the front end. But with Node.js, you know exactly which operations are supported by Google’s V8 JavaScript engine. So, you can directly use these built in functions for manipulating collections on the server side.

9. Use nginx in Front of Node

Nginx is a tiny and lightweight web server that can be used to reduce the load on your Node.js server. Instead of serving static files from Node, you can configure nginx to serve static content. You can also set up nginx to compress the response using gzip so that the overall response size is small. So, if you are running a production app you might want to use nginx to improve the speed.

10. Minify and Concatenate JavaScript

Finally, your web app speed can be tremendously increased by minifying and concatenating multiple JS files into one. When the browser encounters a <script> element the page rendering is blocked until the script is fetched and executed (unless async attribute is set). For example, if your page includes five JavaScript files, the browser will make five separate HTTP requests to fetch those. The overall performance can be hugely improved by minifying and concatenating those five files into one. The same applies to CSS files as well. You can use a build tool like Grunt/Gulp to minify and concatenate your asset files.

Conclusion

These 10 tips can surely improve your web app speed. But, I know there is still room for more improvements and optimizations. Let us know in comments if you have any such performance improvement tips.

Thanks for reading!

JavaScript: Novice to Ninja, 2nd Edition