A few decades ago when the first architecture books were being written, today's large-scale web systems were an oddity, but now they are mainstream. Our architecture pattern languages have changed as have our development, deployment, and operating procedures. During this transition, one source of ideas has been the functional programming (FP) community. FP itself mostly happens within a module, and many software architects treat it as an implementation choice, unrelated to architecture. But some ideas from the FP community are helpful in architectural design: statelessness, immutability, and pure functions. They underlie DevOps practices and are at the core of many distributed systems patterns in our architectures. Although functional programming ideas have been around for a long time, conditions are ripe for applying them now. This talk surveys how modern web systems are built with FP patterns, shows how they work, and considers why they are increasingly popular. We will dig into one client-side example and demonstrate how FP ideas can simplify tasks.
