Clojure has been heralded as a pioneer in data oriented functional programming. In this talk, Huahai will explore the use of Clojure data diffing/patching library as a tool to simplify software architecture and solve complex engineering problems. After briefly describing EditScript, a Clojure data diffing/patching library, he will detail several usage patterns by drawing from code examples in our production system. Huahai will discuss how diffing improves system modularization by reducing namespace dependencies; how it drastically simplifies client-server communication to drive much faster UI iterations; how it enables massive scaling by turning stateful applications into stateless ones; and how it powers collaborative editing of online documents. This talk is for everyone who are interested in expanding their data oriented functional programming tool box.