Ratpack is a set of libraries for developing fast, efficient, evolvable and well tested HTTP applications written in Java 8 or any alternative JVM language that plays well with Java, such as Groovy. The session will start with an introduction about Ratpack, and what makes it different from other popular frameworks like Grails or Vert.x, to name a few. Then, it will cover the fundamentals of the async programming model used in Ratpack applications, as well as other core concepts like handlers and the registry. Also, some of of the core modules ("plug-ins") will be described. Finally, it will cover how to test Ratpack applications using Groovy and Spock.