Connect a NestJS application to Neon

NestJS is a framework for building efficient, scalable Node.js server-side applications¹. This guide explains how to connect NestJS with Neon using a secure server-side request.

To create a Neon project and access it from a NestJS application:

1. Create a Neon project
2. Create a NestJS project and add dependencies
3. Configure a Postgres client
4. Run the app

Create a Neon project

If you do not have one already, create a Neon project. Save your connection details including your password. They are required when defining connection settings.

1. Navigate to the Projects page in the Neon Console.
2. Click New Project.
3. Specify your project settings and click Create Project.

Create a NestJS project and add dependencies

1. Create a NestJS project if you do not have one. For instructions, see Quick Start, in the NestJS documentation.

2. Add project dependencies using one of the following commands:

   Neon serverless driver

   postgres.js

   node-postgres

   npm install @neondatabase/serverless

Store your Neon credentials

Add a .env file to your project directory and add your Neon connection string to it. You can find the connection string for your database in the Connection Details widget on the Neon Dashboard. For more information, see Connect from any application.

DATABASE_URL="postgresql://<user>:<password>@<endpoint_hostname>.neon.tech:<port>/<dbname>?sslmode=require"

Configure the Postgres client

1. Create a Database Module

To manage the connection to your Neon database, start by creating a DatabaseModule in your NestJS application. This module will handle the configuration and provisioning of the Postgres client.

import { config } from 'dotenv';
import { Module } from '@nestjs/common';
import { neon } from '@neondatabase/serverless';

// Load Environment Variables
config({
  path: ['.env', '.env.production', '.env.local'],
});

const sql = neon(process.env.DATABASE_URL);

const dbProvider = {
  provide: 'POSTGRES_POOL',
  useValue: sql,
};

@Module({
  providers: [dbProvider],
  exports: [dbProvider],
})
export class DatabaseModule {}

2. Create a Service for Database Interaction

Next, implement a service to facilitate interaction with your Postgres database. This service will use the database connection defined in the DatabaseModule.

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

@Injectable()
export class AppService {
  constructor(@Inject('POSTGRES_POOL') private readonly sql: any) {}

  async getTable(name: string): Promise<any[]> {
    return await this.sql(`SELECT * FROM ${name}`);
  }
}

3. Integrate the Database Module and Service

Import and inject the DatabaseModule and AppService into your AppModule. This ensures that the database connection and services are available throughout your application.

import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { DatabaseModule } from './database/database.module';

@Module({
  imports: [DatabaseModule],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

4. Define a Controller Endpoint

Finally, define a GET endpoint in your AppController to fetch data from your Postgres database. This endpoint will use the AppService to query the database.

import { Controller, Get } from '@nestjs/common';
import { AppService } from './app.service';

@Controller('/')
export class AppController {
  constructor(private readonly appService: AppService) {}

  @Get()
  async getTable() {
    return this.appService.getTable('playing_with_neon');
  }
}

Run the app

When you run npm run start you can expect to see output similar to the following at localhost:3000:

[{"id":1,"name":"c4ca4238a0","value":0.39330545},{"id":2,"name":"c81e728d9d","value":0.14468245}]

Source code

You can find the source code for the application described in this guide on GitHub.

• Get started with NestJS and Neon

  Get started with NestJS and Neon