Square manages big data, high uptime, secure payment info and large teams in an agile Rails environment. It's hard. Our system has outgrown the patterns of a young Rails app and some of what used to help has started to hurt. It's painful to have your email templates in the same project as your API backend. It's agonizing to use your main datastore for analytics, and it hurts to throw code into ./lib or require unnecessary gems. This talk is about how we've turned individual Rails pieces into separate services and scaled our codebase, data, and integration testing practices to support multiple big teams efficiently.