Express Deployment Guide#

This guide explains how to deploy Node.js backend applications using Express via Atlas. Atlas currently supports deploying Express services and APIs primarily to Render.

1. Project Detection#

Atlas determines your project is an Express application by detecting express in the dependencies of your package.json.

2. Server Entry Point & Scripts#

Unlike frontend frameworks that have a definitive build step, Express apps require a reliable start command. Your package.json must include a start script.

"scripts": {
  "start": "node index.js"
}

• No Build Step: If you are using raw JavaScript, Atlas will skip the build step and proceed directly to deployment.
• TypeScript: If you are using TypeScript with Express, you must include a build script (e.g., tsc) and ensure your start script points to the compiled output (e.g., node dist/index.js). Atlas will automatically run the build script if it exists.

3. Port Configuration#

When deploying to a cloud provider like Render, your application must listen on the port assigned by the provider via the PORT environment variable.

Ensure your Express app respects process.env.PORT:

const express = require('express');
const app = express();

// Use the PORT environment variable provided by the cloud host
const port = process.env.PORT || 3000;

app.listen(port, () => {
  console.log(`Server is running on port ${port}`);
});

If you hardcode a port (like 3000), your deployment will fail health checks on Render. If Atlas detects a hardcoded port failing the build/health check, the auto-fix engine may automatically patch your code to use process.env.PORT.

4. Databases and Secrets#

Express apps frequently connect to databases (PostgreSQL, MongoDB, etc.).

• When deploying to Render, Atlas can automatically provision a managed PostgreSQL database and attach the resulting DATABASE_URL directly to your Express service's environment.
• Make sure you use environment variables (e.g., process.env.DATABASE_URL, process.env.JWT_SECRET) instead of hardcoding secrets into your source code.