In general, designing and creating a computer system is a balancing act. We're constantly trying to add features and capabilities while keeping the code simple and the system's performance reasonable. In this respect, data analysis systems are no different. In fact, they may be worse. Often data is only partially consistent, and we need to employ a variety of strategies to extract usable data before we can even begin its analysis. Each added strategy adds a little more complexity, weight, and bloat to the code, each of which makes it a little harder to maintain. This can get out of hand.

Clojure has a number of libraries to help us manage our systems' complexity. One of the most powerful of these is concurrent programming. This allows us to conceptualize our programs differently and in ways that can help manage the complexity. Instead of having monolithic blocks of code that do many things and have direct, tight dependencies, we can structure our program more modularly by composing...