Deep modules

Hide useful behavior behind a small interface. Apply this as a design lens while preserving the project's vocabulary and established architecture.

Terms

• Module: an interface and its implementation, from a function to a larger subsystem.
• Interface: what callers must know, including types, invariants, ordering, errors, configuration, and performance.
• Depth: useful behavior hidden relative to the interface a caller must learn.
• Seam: a point where behavior can be substituted without editing callers.
• Adapter: an implementation that translates or supplies behavior at a seam.
• Locality: how closely a change, its consequences, and its verification stay together.

Use the project's terms such as service, component, API, or boundary when they carry the intended meaning. Do not rename concepts merely to adopt this glossary.

Evaluate the interface