Clojure offers a principled approach to designing systems by making data front and center. Data is not about juggling values in memory; data is about communication, agreement, tolerance, change management, and more. This talk will focus on how Clojure's flavor of dynamic functional programming helps in designing systems. Christophe is a long-time Clojure enthusiast. He put it into production 9 years ago and has worked exclusively in it for 6 years. The entire time, he has been an independent software engineer/trainer/consultant working from the French countryside. He co-authored O'Reilly's Clojure Programming and numerous libs.