Is it possible to implement the singleton pattern within the NestJS framework?

Yes, in NestJS, the singleton pattern is implemented by default for services and providers. When you create a service and register it in a module, NestJS creates a single instance of that service, which is then injected into all components where it is required.

This is achieved through the built-in Dependency Injection mechanism and the provider container.

Example:

import { Injectable } from '@nestjs/common';

@Injectable()
export class MySingletonService {
  private counter = 0;

  increment() {
    this.counter++;
    return this.counter;
  }
}

// In any component where MySingletonService is injected, there will be the same instance