In software design, abstraction is a two-edged sword: It can enable reuse, create powerful generalizations, yield flexible models, and enhance domain understanding. It can also result in incomprehensible and unmaintainable code messes and poor alignment of domain and architecture. Thus, it’s no surprise that modern DDD practice tends to shy away from abstraction. We’ll examine the benefits and tradeoffs of abstraction at an architectural level. More importantly, we’ll look at techniques for systematic abstraction that avoid the pitfalls, and show how you can use them to maximum architectural effect and (maybe more importantly) better software for its users. As always, functional programming plays a role.