db.module.ts

import { DatabaseService } from './db.service';
import { Global, Module } from '@nestjs/common';

@Global()
@Module({
  providers: [DatabaseService],
  exports: [DatabaseService],
})
export class DbModule {}

db.service.ts

import { Injectable } from '@nestjs/common';
import * as AWS from 'aws-sdk';

@Injectable()
export class DatabaseService {
  connect(): AWS.DynamoDB.DocumentClient {
    return process.env.IS_OFFLINE
      ? new AWS.DynamoDB.DocumentClient({
          region: 'localhost',
          endpoint: process.env.DYNAMODB_ENDPOINT,
        })
      : new AWS.DynamoDB.DocumentClient();
  }
}