Building Production Backends with NestJS

My focus for this month of October will be on NestJS framework and how it has imparted my development experience as a fullstack software engineer. NestJS provides a structured framework for building Node.js applications, but the framework alone does not determine whether an application will be maintainable in production.

The architecture surrounding the framework matters a lot. I will be sharing overview on my opinions when developing a secure and scalable systems in NestJS.

Feature-oriented modules

I prefer organizing backend systems around business capabilities rather than technical file types.

For example:

src/ ├── modules/ │ ├── users/ │ ├── authentication/ │ ├── payments/ │ └── notifications/ │ ├── infrastructure/ ├── shared/ └── main.ts 

This keeps related business functionality together.

Dependency boundaries

Business logic should not directly depend on infrastructure details.

For example, application code should depend on an abstraction:

export interface EmailSender { send(message: EmailMessage): Promise<void>; } 

rather than directly depending on a specific provider.

The infrastructure layer can then implement it:

export class ResendEmailSender implements EmailSender { async send(message: EmailMessage): Promise<void> { // provider implementation } } 

This makes it possible to replace infrastructure without rewriting business logic.

The goal

The goal is not to create the largest possible architecture.

The goal is to create a system where important decisions remain easy to change.

That principle becomes increasingly important as an application grows.