Managing Complexity
As systems engineers, we must build and integrate elements and subsystems to achieve a desired objective. There can be a lot of moving parts: various APIs and communication protocols, various data schemas, various security interfaces to traverse. Our biggest challenge is, How do we manage all this complexity?
The best tool for the job
The best tool we have  to help manage complexity is composition. Functional programming to the rescue!
Our job is to decompose the elements of our system into atomic parts, fit them back together into subsystems and wire them together in a distributed, microservice based environment.
How do we know when have we sufficiently decomposed an element?
A: When we can treat the element as a black box, i.e., when we do not need visibility into the function to understand what it does.
Divide and conquer
FP gives us the tools and techniques we need to divide our monolithic applications into microservices.
In Chapter 4, SOLID Design in Go, we learned that...