Why I migrated from Nest.js to Fastify and DDD in 2026

In the fast-paced world of backend development, choosing the right framework can make the difference between an agile project and a tangle of dependencies. For years, Nest.js was my preferred choice for its enterprise structure, native TypeScript support, and Spring-style dependency injection. However, as projects scaled and complexity increased, I began to question whether so much abstraction truly added value or simply added friction. In 2026, I made the firm decision to migrate my projects to Fastify combined with Domain-Driven Design (DDD). This is not an absolute judgment on Nest.js, but a personal analysis of the trade-offs that, for my workflow, proved unsustainable. The promise of order and standardization faded in the face of layers of decorators, magical wrappers, and fragile dependencies that slowed down debugging and code evolution. By switching to Fastify, I regained lightness and transparency: the framework limits itself to handling HTTP without imposing a rigid architecture. This, combined with DDD principles —where the business domain is the center and technical adapters are mere details— allowed me to build custom applications that are much more maintainable and testable. For example, a controller in Fastify is just a route handler that delegates to an application service; a repository is a TypeScript class without decorators. The separation between business logic and the framework is so clean that I can change infrastructure without touching the core. Additionally, debugging is simplified: stack traces point directly to the source file, without having to traverse layers of generated metadata. This clarity is especially valuable when integrating complex systems, such as cloud services aws and azure, or when enabling artificial intelligence capabilities and AI agents for businesses. At Q2BSTUDIO, we understand that each project requires a pragmatic approach. Therefore, when evaluating the architecture of our developments, we prioritize flexibility and reduction of technical debt. We do not rule out Nest.js in teams that value its conventions, but for those who need custom software with high performance and granular control, Fastify+DDD has become our standard. We have also seen how this solid foundation facilitates the inclusion of business intelligence services like Power BI, and the implementation of cybersecurity from the design stage, preventing the framework from overshadowing good practices. Artificial intelligence for businesses, AI agents, and process automation benefit from an architecture where the domain is sovereign and middleware is explicit. If you are considering a similar change or wish to build robust and scalable systems, we invite you to explore how we combine these technologies to offer solutions that truly adapt to your needs. The migration was not just technical: it was a rediscovery of simplicity as a competitive advantage.