Most mobile apps require a back-end. Sometimes the backend is written by another team, but often it is built and maintained by the same team creating the mobile app. These back-ends are not websites; they are usually just a few endpoints. Ratpack is a perfect solution for creating such endpoints. Ratpack is a set of libraries for building HTTP apps. It is not an opinionated and bulky framework with lots of settings to configure and code to write. Creating Ratpack apps in Kotlin, with its sleek coding style, makes the experience even more enjoyable. In this talk, we demonstrate building an isomorphic Kotlin mobile system. Starting with a functional Android app, we'll create the backend in Ratpack using Kotlin and wire up a few endpoints, then call them. Once we are happy with our backend, we will deploy it to Heroku. Android developers will learn how Kotlin makes it easier to create web services for your app. Troy Miles, aka the Rockncoder, began writing computer games in assembly language for early computers like the Apple II, Commodore C64, and the IBM PC over 35 years ago. Nowadays he writes web & mobile apps for a Southern California based automotive valuation and information company. Troy is fluent in JavaScript, C#, C++, Kotlin, and Clojure. On nights and weekends he can usually be found writing cool apps for mobile and web or teaching others how to do so. Troy has spoken at O'Reilly's Velocity, MobileWeb Dev Con, Mobile Dev+Test, and NG-Vegas. He is a regular speaker at So Cal and Silicon Valley Code Camps and to local developer groups all over southern California and Las Vegas. A few of his talks can be found on his YouTube channel: https://www.youtube.com/user/rockncoder. Troy loves writing about software development. His first magazine article was published in Dr. Dobb's magazine over twenty years ago. He is the author of jQuery Essentials. Troy is now a video author on Lynda.com and is working on his first title.