Pattern: Deep modules

John Ousterhout’s principle: a good module provides “a lot of functionality accessed through a simple interface.” Maximize the ratio of capability to interface surface, and place module boundaries at clean seams — the antidote to architectural entropy (“ball of mud”).

Applied by (backlinks)

Matt Pocock — Skills for Real Engineers:

• mp-codebase-design — design discipline for deep modules with small interfaces.
• mp-improve-codebase-architecture — audits existing code toward this shape.

Addy Osmani — Agent Skills:

• addy-api-design — designs small interfaces over rich functionality.

Compound Engineering:

• ce-simplify-code — reduce complexity / extract reuse behind simpler interfaces, behavior-preserving.
• ce-architecture-strategist — reviews module boundaries / service boundaries for integrity.

See Also

• stage-plan — where forward-looking design applies.
• stage-review — where the architecture audit applies.