An architectural doctrine for NestJS projects: a breakdown of typical codebase degradation scenarios and the structural constraints that keep them from emerging as the feature set grows.

In parts 1–2 we watched a simple signUp turn, under the pressure of requirements, into a god-service of hundreds of lines that knew about a dozen modules at once. In part 3 we worked through how forwardRef and circular dependencies are born from this naturally — that very tangle that can no longer be untangled. In part 4 we designed an FBCA architecture from scratch — domain / use-case / infrastructure / presentation with layers, external ports, and Result-based error handling — and showed how the same signUp looks inside it.

Part 5 is a parallel universe of the same plot.…