NestJs for lambda with mongodb creating too many connections

We are using nestjs for lambda which connects with mongodb for data. We are using nestjs mongoose module. However on deployment for each invocation a new set of connection are made and the previous ones are not released.

We are using forRootAsync

MongooseModule.forRootAsync({
      useClass: MongooseConfigService,
    })

service looks like this:

@Injectable({ scope: Scope.REQUEST })
export class MongooseConfigService implements MongooseOptionsFactory {
  constructor(@Inject(REQUEST) private readonly request: Request) {}

  async createMongooseOptions(): Promise<MongooseModuleOptions> {
    if (Buffer.isBuffer(this.request.body)) {
      this.request.body = JSON.parse(this.request.body.toString());
    }
    const { db } = this.request.body;
    console.log('connecting database', db);
    return {
      uri: process.env.MONGO_URL,
      dbName: db || '',
    };
  }
}

I understand we need to reuse the same connection. We have achieved it in nodejs by simply checking if the connection already exists and if it does not connect again. Not sure how to achieve the same in nest.js

tried changing the scope of service to Scope.DEFAULT but that didn’t help.