Key Points

• Switching to production mode can significantly improve Express application performance, because production mode eliminates logging and exception stack trace tasks in development mode.
• Enable GZIP compression in Express 4.x can reduce HTTP load and improve performance. This can be done by installing the compression module and using it as the first middleware function.
• Removing unnecessary middleware, considering using a simpler template engine, and effectively caching common variables can further optimize the performance of Express applications. Build tools such as Gulp can be used to compress and merge HTML templates, CSS, and JavaScript files, and session variables should be restricted to avoid memory-related performance issues.

Node.js has completely changed web development, and the Express framework has made an indelible contribution. Express may not be the fastest or most advanced server option, but it is almost certainly the most widely used, with over 3 million downloads per month. If you do nothing, Node.js and Express will also run very quickly. However, there are some easy ways to make Express 4.x run faster...

1. Switch to production mode

Express can be run in multiple modes. By default, it assumes to be development mode, which provides exception stack traces and other logging tasks. There is also a debug mode that logs messages to the console, for example:

<code>DEBUG=express:* node ./app.js</code>

On your live server you can significantly improve performance by switching to production mode. This can be done by setting the NODE_ENV environment variable to production. It can be set in the current session of Windows before starting the Express application:

<code>set NODE_ENV=production</code>

or Mac/Linux:

<code>export NODE_ENV=production</code>

Linux users can also set NODE_ENV in a line at startup:

<code>NODE_ENV=production node ./app.js</code>

Ideally, you should configure your environment by adding <code>export NODE_ENV=production</code> to your ~/.bash_profile or the corresponding startup script.

2. Enable GZIP

Express 4.x provides the least amount of available features that can be enhanced with middleware. A less obvious missing feature is GZIP compression, which reduces the HTTP load so that the browser can scale it when it receives. To add GZIP, use npm to install the compression module:

<code>npm install compression --save</code>

(Depending on your setup, you may need to use sudo on Mac/Linux – there are many ways to solve this problem.) In your main application startup file, include the compression module:

<code>var compression = require('compression');</code>

Then install it as the first middleware function (before other Express .use methods):

<code>DEBUG=express:* node ./app.js</code>

3. Delete unnecessary middleware

If you generated a prebuilt application using Express Generator or similar procedures, delete any middleware modules you did not use. For example, if you do not use cookies, you can delete the cookie-parser module or use req.cookies and res.cookies to implement a simpler alternative. In production mode, some processes can be deleted, such as debug output, for example:

<code>set NODE_ENV=production</code>

In other words, it is best to keep serve-favicon. The browser frequently requests the favicon.ico file, and the module can improve caching.

4. Consider using a simpler template engine

Jade is the default template engine for many Express installations, and it is a good choice. However, if you are happy to write your own HTML and only need basic interpolation and evaluation, consider using a lightweight alternative, such as doT, which can be added as Express middleware using the express-dot-engine module. Alternatively, you can bypass the template engine for a simpler response, such as:

<code>export NODE_ENV=production</code>

Always make sure view caching is enabled regardless of which template engine you are using:

<code>NODE_ENV=production node ./app.js</code>

5. Remember cache!

Unlike most server-based applications, the Node.js application runs permanently. So you can set common variables like database connection objects once and reuse them during each request for each user. This concept can be expanded as needed. Generally speaking, the more common items you can cache, the better the performance. For example, suppose your Express-based CMS application shows links to your last five posts on the homepage. The list can be generated and stored in a variable and is only updated when new articles are published.

Extra quick tips

Want more? …

• Consider using nginx to serve static content and reduce the load on Node.js and Express.
• Use build tools such as Gulp to compress and merge your HTML templates, CSS, and JavaScript files.
• Limit the use of session variables. User session data is usually stored in memory, which can lead to performance issues as usage increases. Consider using only IDs and then obtaining user information from the database during the request.
• Increase the maximum number of HTTP sockets from five to higher numbers, for example:

<code>npm install compression --save</code>

• When possible, call blocking sequences of operations instead of sequentially.
• Avoid using synchronous blocking calls in everything except application initialization.
• Always note that code runs for one user blocks code run for each other user.

Do you have other performance tips for Node.js or Express? I'd love to hear them in the comments.

(The chapter on FAQs on Node.js performance tuning should be added here, the same content as provided in the input text)

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