just enough architecture - Partitioning in architecture

src: Just Enough Software Architecture: A Risk-Driven Approach by George H. Fairbanks | Goodreads

Abstract

Partitioning is effective as a strategy to combat complexity and scale when two conditions are true: first, the divided parts must be sufficiently small that a person can now solve them; second, it must be possible to reason about how the parts assemble into a whole. Parts that are encapsulated are easier to reason about, because you need to track fewer details when composing the parts into a solution. You can forget, at least temporarily, about the details inside the other parts. This allows the developer to more easily reason about how the parts will interact with each other.