Use when organizing a shared backend infrastructure library that many services depend on (e.g. @org/infra-*) — how to split it into focused packages by dependency weight, expose one barrel per package, avoid dependency cycles with peer deps, version/publish it, decide what belongs in the lib vs a service, and the canonical primitives it should provide (a base entity with soft-delete + audit columns, base pagination/response DTOs, column transformers, type helpers). NestJS/TypeORM reference, framework-flexible. The backend twin of structure-a-shared-ui-lib.
