A modular architecture
Modules, controllers, services and dependency injection, in the spirit of Angular, give each feature a clear place and make the code easier to take over.
Expertise · NestJS
NestJS Development: a structured TypeScript back end built to last
Etixio delivers NestJS development for your TypeScript back ends: APIs and services designed to evolve with your product. We build new platforms, take over and restructure existing ones, and build the services that orchestrate AI models and agents in your application.
Understanding the technology
NestJS in your project.
NestJS is a framework for building server-side applications with TypeScript. It provides an organization into modules and dependency injection mechanisms. This structure helps distribute the responsibilities of an API or a set of services, provided the modules match the product’s needs.
The strengths for your product
Why choose NestJS?
NestJS brings to Node.js the structure that JavaScript back ends often lack as the product grows. It suits business applications, SaaS platforms and service-based architectures.
TypeScript end to end
Static typing, decorators and DTOs make contracts explicit and make refactoring safer.
Ready-to-use patterns
Microservices, CQRS, GraphQL, WebSockets, scheduled tasks and configuration are built into the framework or its official modules.
Built-in testing
The NestJS structure makes services testable in isolation, with Jest for unit tests and Supertest for end-to-end tests.
Our scope of work
The work we take on.
Modules
Define the features, dependencies and interfaces of services.
APIs
Define contracts, data validation and access rights.
Tests
Verify services in isolation, then their exchanges with databases and client applications.
Our NestJS expertise
The NestJS ecosystem we master.
Framework core
Nest CLI, module and provider system, decorators, guards, validation pipes and interceptors.
Architecture
Microservices with TCP, Redis or NATS transports, CQRS, domain-driven design when business complexity justifies it.
Data
TypeORM, Prisma or Mongoose, migrations, transactions and connection pools, on PostgreSQL, MySQL or MongoDB.
Communication
REST APIs documented with OpenAPI / Swagger, GraphQL with Apollo, WebSockets and gRPC.
NestJS is built on Node.js and uses Express or Fastify as its HTTP layer.
NestJS and AI
Orchestrating models and agents in a NestJS back end.
A product’s AI features benefit from being treated like any other module: a dedicated module calls the models, exposes the agent’s tools as services, applies authorization guards and logs every exchange. Responses can be streamed to the interface, and long-running tasks offloaded to processing queues.
We build these modules, with evaluations, cost tracking and monitoring, and take over AI prototypes to integrate them cleanly into your back end. See our AI agents and chatbots and our enterprise AI solutions.
In the field
From technology to real-world use.
In a subscription management service, we separate access rules, billing and exchanges with the payment provider. Incoming data is validated, and external events can be processed several times without creating multiple subscriptions. Tests cover the business services and the integrations that actually trigger state changes.
The choices that matter
The choices to examine before building.
Splitting code into modules does not by itself solve circular dependencies or poorly defined business boundaries. We examine contracts, responsibilities and transaction needs. The choice of transport or asynchronous processing remains tied to usage and the expected operating conditions.
From work to deliverables
Delivery your team can take over.
The scope of the engagement specifies the components to build or take over and the acceptance criteria. We deliver in short iterations, with continuous integration and code reviews, through to production release and maintenance. We prepare what is needed to understand the changes, verify them and continue the work.
- Services and API contracts
- Business rule tests
- Deployment procedures
Frequently asked questions
NestJS development: your questions.
What is NestJS and why use it?
NestJS is a Node.js framework in TypeScript that provides a modular structure, dependency injection and well-established patterns. It suits complex projects that must remain maintainable over several years.
Is NestJS suited to enterprise applications?
Yes. Its modular architecture, TypeScript and testing tools make it a good choice for business applications, SaaS platforms and microservice architectures.
What is the difference between NestJS, Express and Fastify?
NestJS uses Express or Fastify as its HTTP server and adds an architecture, dependency injection and conventions on top. Express and Fastify are lighter and leave the organization to the team; NestJS is preferable as the project and the team grow.
How do you structure a NestJS application?
By functional modules, with controllers for HTTP, services for business logic and repositories for data. DTOs carry validation, guards handle authentication and interceptors handle logging.
Does NestJS handle databases well?
Yes, with TypeORM, Prisma, Mongoose or Sequelize. Transactions, migrations, relationships and multiple databases within the same application are supported.
How do you handle authentication in NestJS?
With guards for authentication and roles, Passport integration, JWT tokens and OAuth2. Authorization rules remain testable like the rest of the code.
How do you test a NestJS application?
Unit tests of services with mocked providers, end-to-end tests on the running application with Supertest, test datasets and an isolated test environment, all run in continuous integration.
Can an AI agent be integrated into a NestJS back end?
Yes. The agent becomes a module that calls the model and uses existing services as tools, under the control of the application’s guards and logs. We add evaluations, cost tracking and monitoring for production.
What collaboration models do you offer?
A fixed-price project for a defined scope, a dedicated team to evolve your back end over time, or a targeted engagement (architecture, migration to NestJS, performance).
Let’s talk about your technical context.
Tell us about the application, the issue to address and the known constraints. We will review the dependencies and the first scope of work with your team.