Web applications are becoming the norm for users, and being able to handle thousands of requests per second is happening more and more. Developers spend an enormous amount of time making sure that their applications are as fast as possible, but tuning your web server can only go so far. Async Programming is being used by many languages as a quick and easy way to serve web applications, and PHP is no exception. Libraries like ReactPHP and Amp, alongside extensions like Swoole, give developers broad choices for how to build their applications using async principles. See how these tools and async programming can help your application stay quick and agile.