Designs and reviews NestJS application architecture using cohesive feature modules, modular monoliths, layered or hexagonal boundaries, dependency inversion, and pragmatic engineering principles. Use when planning a NestJS project, changing module boundaries, evaluating Clean Architecture or DDD, resolving circular dependencies, defining ports and adapters, reviewing coupling, or deciding whether CQRS or microservices are justified. Do not use for pure frontend work or non-NestJS backends. When other skills also apply, reconcile ownership before mutation.
