At the core of every major Ruby web framework is Rack, a slim, versatile HTTP library. In this course, Building Ruby Web Apps with Rack, you'll learn how to use Rack and make simple, fast web applications. First, you'll learn the basic protocol that Rack uses for communicating with web servers like Puma and Unicorn. Next, you'll discover how to extend and enrich your application with middleware. Finally, you'll explore how to leverage your knowledge of Rack in other frameworks like Rails and Sinatra. When you're finished with this course, you'll have a foundational knowledge of Rack that will help you build faster, more maintainable Ruby web applications.