Introduction

Building a full-stack application with Next.js and PostgreSQL is a powerful choice for modern web development. But when it comes to deployment, costs can quickly add up. Traditional VPS hosting requires maintenance, and managed databases often come with a hefty price tag.

Fortunately, the modern "Serverless" ecosystem offers a solution. By combining Vercel (for the frontend and API) with Neon (for a serverless PostgreSQL database), you can deploy a scalable, production-ready full-stack application completely for free.

In this guide, we will walk through the exact process of deploying a Next.js 15 application with Prisma ORM and Auth.js (NextAuth), covering every step from database creation to handling common deployment errors.

The Tech Stack

• Framework: Next.js 15 (App Router)
• Database: PostgreSQL
• Infrastructure: Vercel (Frontend/API Hosting) + Neon (Serverless Database)
• ORM: Prisma
• Authentication: NextAuth.js (Google OAuth)

Step 1: Set Up Your Serverless Database with Neon

The first hurdle in full-stack deployment is the database. Neon separates storage from compute, allowing it to "scale to zero" when not in use, making it perfect for free-tier projects.

1. Create a Project: Go to Neon.tech, sign up, and create a new project.
2. Get Connection Details:
   • Neon provides a Pooled Connection string (optimized for serverless apps like Next.js).
   • It also provides a Direct Connection string (needed for database migrations).
   • Keep both handy! You will need them significantly in Step 3.

Pro Tip: Using a pooled connection for your live app prevents "max connection" errors, which are common when serverless functions scale up.

Step 2: Prepare Your Next.js Application

Before deploying, ensure your project is configured to handle the production environment.

1. Prisma Schema Configuration

Serverless environments have a quirk: they don't play well with long-running connections during database migrations. To fix the common P1002: Timed out trying to acquire a postgres advisory lock error, you must separate your migration connection from your app connection.

Update your 

prisma/schema.prisma:

datasource db {
  provider  = "postgresql"
  url       = env("DATABASE_URL") // Pooled connection for the app
  directUrl = env("DIRECT_URL")   // Direct connection for migrations
}

2. The Build Script

Ensure your 

package.json includes a build script that generates the Prisma client and runs migrations automatically during deployment:

"scripts": {
  "build": "npx prisma generate && npx prisma migrate deploy && next build"
}

This ensures that every time you deploy, your database schema is up-to-date.

Step 3: Deploying to Vercel

Vercel is the creators of Next.js, offering the smoothest deployment experience.

Option A: The "No-Git" CLI Method (Fastest)

If you don't want to mess with creating a GitHub repository yet, you can deploy directly from your terminal.

1. Install Vercel CLI: npm i -g vercel
2. Login: npx vercel login
3. Deploy: Run npx vercel --prod inside your project folder.
4. Follow the prompts to link your project.

Option B: The GitHub Method (Recommended)

1. Push your code to a GitHub repository.
2. Log in to Vercel and click "Add New Project".
3. Import your repository.

Step 4: Configuring Environment Variables

This is where most deployments fail. Your application needs the secrets to connect to the database and authentication providers.

In your Vercel Project Dashboard, go to Settings > Environment Variables and add the following:

Critical Note: Do NOT confuse DATABASE_URL and DIRECT_URL. If you swap them,

your app might work, but your deployments will fail randomly with timeout errors.

Step 5: Handling Authentication (Google OAuth)

If your app uses Google Login, it will break immediately after deployment because Google doesn't trust your new domain yet.

1. Go to the Google Cloud Console.
2. Navigate to APIs & Services > Credentials.
3. Edit your OAuth 2.0 Client.
4. Add your Vercel domain (e.g., https://myapp.vercel.app) to Authorized JavaScript origins.
5. Add the callback path (e.g., https://myapp.vercel.app/api/auth/callback/google) to Authorized redirect URIs.

Wait a few minutes for Google to propagate changes.

Troubleshooting Common Errors

1. P1002: Timed out trying to acquire a postgres advisory lock

Cause: You are running prisma migrate deploy using a pooled connection. Fix: Ensure you added the directUrl field in your Prisma schema (Step 2) and defined the DIRECT_URL environment variable pointing to the non-pooled Neon string.

2. 404 Not Found on Vercel

Cause: Vercel might be deploying the wrong directory (often happened if you imported a monorepo). Fix: Go to Settings > General > Root Directory and ensure it points to your Next.js app folder usually (./ or your-app-name). Alternatively, deploy using the CLI command npx vercel --prod from the correct folder.

3. Error: No Output Directory named "public"

Cause: Vercel thinks your project is a static site, not a Next.js app. Fix: Create a 

vercel.json file in your root:

{
  "framework": "nextjs",
  "buildCommand": "npx prisma generate && npx prisma migrate deploy && next build"
}

Conclusion

You now have a professional-grade, full-stack application running for $0/month. This architecture scales effortlessly: Vercel handles global traffic distribution and caching, while Neon manages your database scaling.

By following this guide, you’ve not only deployed an app but built a robust foundation for any future SaaS or side project. Happy coding!