backend-architecture

Layered and modular architecture for NestJS and Node services - modular monolith by default, module boundaries and dependency direction, domain vs application vs infrastructure, ports and adapters, DTO/domain/persistence mapping, transaction boundaries, sync vs async communication, events, idempotency, when to split a service, config and feature flags, multi-tenancy, orchestration and BFF layers for chat and AI-style apps, and versioning boundaries. Load when designing service structure, adding a module or integration, deciding sync vs async, or considering splitting a service.