µExpress / Ultimate Express

The Ultimate Express. Fastest http server with full Express compatibility, based on µWebSockets.

This library is a very fast re-implementation of Express.js 4. It is designed to be a drop-in replacement for Express.js, with the same API and functionality, while being much faster. It is not a fork of Express.js.
To make sure µExpress matches behavior of Express in all cases, we run all tests with Express first, and then with µExpress and compare results to make sure they match.

npm install ultimate-express

Difference from similar projects

Similar projects based on uWebSockets:

• express on Bun - since Bun uses uWS for its HTTP module, Express is about 2.5 times faster than on Node.js with 25k req/sec instead of 10k req/sec normally, but still slower than µExpress at 60k req/sec because it doesn't do uWS-specific optimizations.
• hyper-express - while having a similar API to Express, it's very far from being a drop-in replacement, and implements most of the functionality differently. This creates a lot of random quirks and issues, making the switch quite difficult. Built in middlewares are also very different.
• uwebsockets-express - this library is closer to being a drop-in replacement, but misses a lot of APIs, depends on Express by calling it's methods under the hood and doesn't try to optimize routing by using native uWS router.

Performance

Tested using wrk (-d 60 -t 1 -c 200). Etag was disabled in both Express and µExpress. Tested on Ubuntu 22.04, Node.js 20.17.0, AMD Ryzen 5 3600, 64GB RAM.

Also tested on a real-world application with templates, static files and dynamic pages with data from database (nekoweb.org), and showed about 1.5-4X speedup in requests per second.

Differences from Express

In a lot of cases, you can just replace require("express") with require("ultimate-express") and everything works the same. But there are some differences:

• case sensitive routing is enabled by default.
• Depending on how you send response, Content-Length header may be overwritten or not sent at all:
• • on simple responses with res.send(), res.json(), etc. it's set automatically (any value you set with res.set() is overwritten)
• • on streaming responses (piping, res.sendFile()) it's not sent because uWS uses chunked transfer encoding instead
• • on responses without body, it is sent (useful for HEAD requests)
• request body is only read for POST, PUT and PATCH requests by default. You can add additional methods by setting body methods to array with uppercased methods.
• For HTTPS, instead of doing this:

const https = require("https");
const express = require("express");

const app = express();

https.createServer({
    key: fs.readFileSync('path/to/key.pem'),
    cert: fs.readFileSync('path/to/cert.pem')
}, app).listen(3000, () => {
    console.log('Server is running on port 3000');
});

You have to pass uwsOptions to the express() constructor:

const express = require("u-express");

const app = express({
    uwsOptions: {
        // https://unetworking.github.io/uWebSockets.js/generated/interfaces/AppOptions.html
        key_file_name: 'path/to/key.pem',
        cert_file_name: 'path/to/cert.pem'
    }
});

app.listen(3000, () => {
    console.log('Server is running on port 3000');
});

• This also applies to non-SSL HTTP too. Do not create http server manually, use app.listen() instead.

Performance tips

1. µExpress tries to optimize routing as much as possible, but it's only possible if:

• case sensitive routing is enabled (it is by default, unlike in normal Express).
• only string paths without regex characters like *, +, (), {}, :param, etc. can be optimized.
• only 1-level deep routers can be optimized.

Optimized routes can be up to 10 times faster than normal routes, as they're using native uWS router and have pre-calculated path.

2. Do not use external serve-static module. Instead use built-in express.static() middleware, which is optimized for uExpress.

3. Do not set body methods to read body of requests with GET method or other methods that don't need a body. Reading body makes server about 10k req/sec slower.

4. By default, µExpress creates 1 worker thread for reading files (or 0 if your CPU has only 1 core). You can change this number by setting fsThreads to a different number in express(), or set to 0 to disable thread pool for file reading (express({ fsThreads: 0 })). Threads are shared between all express() instances, with largest fsThreads number being used. Using more threads will not necessarily improve performance. Sometimes not using threads at all is faster, please test both options.

Compatibility

In general, basically all features and options are supported. Use Express 4.x documentation for API reference.

✅ - Full support (all features and options are supported)
🚧 - Partial support (some options are not supported)
❌ - Not supported

express

• ✅ express()
• ✅ express.Router()
• ✅ express.json()
• ✅ express.urlencoded()
• ✅ express.static()
• ✅ express.text()
• ✅ express.raw()
• 🚧 express.request (this is not a constructor but a prototype for replacing methods)
• 🚧 express.response (this is not a constructor but a prototype for replacing methods)

Application

• ✅ app.listen()
• ✅ app.METHOD() (app.get, app.post, etc.)
• ✅ app.route()
• ✅ app.all()
• ✅ app.use()
• ✅ app.mountpath
• ✅ app.set()
• ✅ app.get()
• ✅ app.enable()
• ✅ app.disable()
• ✅ app.enabled()
• ✅ app.disabled()
• ✅ app.path()
• ✅ app.param(name, callback)
• ✅ app.param(callback)
• ✅ app.engine()
• ✅ app.render()
• ✅ app.locals
• ✅ app.settings
• ✅ app.engines
• ✅ app.on("mount")
• ✅ HEAD method

Application settings

• ✅ case sensitive routing
• ✅ env
• ✅ etag
• ✅ jsonp callback name
• ✅ json escape
• ✅ json replacer
• ✅ json spaces
• ✅ query parser
• ✅ strict routing
• ✅ subdomain offset
• ✅ trust proxy
• ✅ views
• ✅ view cache
• ✅ view engine
• ✅ x-powered-by

Request

• ✅ implements Readable stream
• ✅ req.app
• ✅ req.baseUrl
• ✅ req.body
• ✅ req.cookies
• ✅ req.fresh
• ✅ req.hostname
• ✅ req.headers
• ✅ req.headersDistinct
• ✅ req.rawHeaders
• ✅ req.ip
• ✅ req.ips
• ✅ req.method
• ✅ req.url
• ✅ req.originalUrl
• ✅ req.params
• ✅ req.path
• ✅ req.protocol
• ✅ req.query
• ✅ req.res
• ✅ req.secure
• ✅ req.signedCookies
• ✅ req.stale
• ✅ req.subdomains
• ✅ req.xhr
• 🚧 req.route (route implementation is different from Express)
• 🚧 req.connection, req.socket (only encrypted, remoteAddress, localPort and remotePort are supported)
• ✅ req.accepts()
• ✅ req.acceptsCharsets()
• ✅ req.acceptsEncodings()
• ✅ req.acceptsLanguages()
• ✅ req.get()
• ✅ req.is()
• ✅ req.param()
• ✅ req.range()

Response

• ✅ implements Writable stream
• ✅ res.app
• ✅ res.headersSent
• ✅ res.req
• ✅ res.locals
• ✅ res.append()
• ✅ res.attachment()
• ✅ res.cookie()
• ✅ res.clearCookie()
• ✅ res.download()
• ✅ res.end()
• ✅ res.format()
• ✅ res.getHeader(), res.get()
• ✅ res.json()
• ✅ res.jsonp()
• ✅ res.links()
• ✅ res.location()
• ✅ res.redirect()
• ✅ res.render()
• ✅ res.send()
• ✅ res.sendFile()
• • ✅ options.maxAge
• • ✅ options.root
• • ✅ options.lastModified
• • ✅ options.headers
• • ✅ options.dotfiles
• • ✅ options.acceptRanges
• • ✅ options.cacheControl
• • ✅ options.immutable
• • ✅ Range header
• • ✅ Setting ETag header
• • ✅ If-Match header
• • ✅ If-Modified-Since header (with options.ifModifiedSince option)
• • ✅ If-Unmodified-Since header
• • ✅ If-Range header
• ✅ res.sendStatus()
• ✅ res.header(), res.setHeader(), res.set()
• ✅ res.status()
• ✅ res.type()
• ✅ res.vary()
• ✅ res.removeHeader()
• ✅ res.write()
• ✅ res.writeHead()

Router

• ✅ router.all()
• ✅ router.METHOD() (router.get, router.post, etc.)
• ✅ router.route()
• ✅ router.use()
• ✅ router.param(name, callback)
• ✅ router.param(callback)
• ✅ options.caseSensitive
• ✅ options.strict
• ✅ options.mergeParams

Tested middlewares

Most of the middlewares that are compatible with Express are compatible with µExpress. Here's list of middlewares that we test for compatibility:

• ✅ body-parser
• ✅ cookie-parser
• ✅ cookie-session
• ✅ serve-static (use express.static() instead for better performance)
• ✅ serve-index
• ✅ cors
• ✅ errorhandler
• ✅ method-override
• ✅ multer
• ✅ response-time
• ✅ express-fileupload
• ✅ express-session
• ✅ express-rate-limit
• ✅ vhost

Middlewares that are confirmed to not work:

• ❌ compression (doesn't error, but doesn't compress)

Tested view engines

Any Express view engine should work. Here's list of engines we include in our test suite:

• ✅ ejs
• ✅ pug
• ✅ express-dot-engine
• ✅ express-art-template
• ✅ express-handlebars
• ✅ swig