As functional programmers we work hard to keep our code compositional and modular. Unfortunately, these noble pursuits often stop with our code, the resulting program flung over the wall to be deployed in complex and prescriptive systems. In this talk we will look at Nelson, a deployment orchestration system that applies functional programming not only in its implementation, but also in its system behavior in managing the messy world of deployment infrastructure. Where Free algebras and streams allow Nelson to be extended to support different VCS platforms, schedulers, and health checkers, Nelson's emphasis on immutable deployments inform system-level decisions such as deployment workflows and service discovery. Having been run successfully at different companies under different configurations, Nelson serves as a prime example of how functional programming can help not just with the software we write, but also with the systems we maintain.