Applying DDD and Hexagonal Architecture to a NestJS API: A Practical Guide

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The guide addresses a common problem in NestJS applications, where services grow to handle business rules, HTTP concerns, and database work together, making changes and testing harder. It uses a service-management API built with TypeScript, NestJS, Prisma, and PostgreSQL as its example, organized into two modules: service-orders and visits. Domain-Driven Design is used to express business behavior as named operations, while Hexagonal Architecture controls dependencies between the business logic and external technologies. The author presents the example as an educational implementation, acknowledging its concrete limitations alongside its benefits. The complete code is published in a GitHub repository called nest-ddd-hexagonal.

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