You have already seen divide and conquer (T8) in Book 1, where large problems are split into smaller problems that can be solved independently and whose solutions are combined. Here it appears at code level as modularity: a codebase is divided into units that can be developed, tested, and deployed independently. The shape is the same — decompose to reduce complexity, recombine to deliver capability. The constraint is the same too: the decomposition is only useful if the pieces genuinely do not depend on each other’s internals.