How do you deploy Next.js applications?

Deploying Next.js applications is a common topic in technical interviews, and it’s something I’ve done multiple times across different projects and environments. The process might seem straightforward at first glance, but there are several nuances that can impact performance, scalability, and maintainability. I’ll walk you through how I approach deploying Next.js apps, including practical tips, common pitfalls, and comparisons with alternative deployment strategies.

Understanding Next.js Deployment Basics

Next.js is a React framework that supports multiple rendering methods: Static Site Generation (SSG), Server-Side Rendering (SSR), and Incremental Static Regeneration (ISR). This flexibility means deployment isn’t one-size-fits-all. Your deployment strategy depends heavily on how your app is built and what features you use.

At a high level, deploying a Next.js app means making your application accessible to users by hosting the compiled output on a server or platform. The build step generates optimized JavaScript, CSS, and HTML, which can be served statically or dynamically depending on your rendering mode.

Core Deployment Modes in Next.js

• Static Export (SSG): Pre-renders all pages at build time into static HTML files. Ideal for blogs, marketing sites, or documentation.
• Server-Side Rendering (SSR): Pages are rendered on-demand on the server for every request. Useful for dynamic content that changes frequently.
• Incremental Static Regeneration (ISR): Hybrid approach where static pages can be updated after deployment without rebuilding the entire site.

Each mode influences how you deploy. Static sites can be hosted on any static file server or CDN, while SSR requires a Node.js server or serverless functions.

Common Deployment Platforms for Next.js

There are several popular platforms for deploying Next.js apps, each with pros and cons:

Platform	Supports SSR	Supports SSG	Ease of Use	Scalability	Cost
Vercel	Yes	Yes	Very Easy	High (Serverless)	Free tier + pay as you go
Netlify	Limited (via serverless functions)	Yes	Easy	Medium	Free tier + paid plans
AWS Amplify	Yes (via Lambda)	Yes	Moderate	High	Pay as you go
Custom Node.js Server (e.g., AWS EC2, DigitalOcean)	Yes	Yes	Complex	Depends on setup	Variable

In my experience, Vercel is the most seamless platform for Next.js since it’s made by the same team and supports all Next.js features out of the box, including ISR and API routes. However, for enterprise or custom infrastructure, hosting on your own servers or cloud VMs might be necessary.

Step-by-Step Deployment Example on Vercel

Here’s a typical workflow I follow when deploying a Next.js app to Vercel:

1. Connect your Git repository: Vercel integrates directly with GitHub, GitLab, or Bitbucket. You push your code, and Vercel triggers a build automatically.
2. Configure build settings: Usually, Vercel detects Next.js apps automatically, running next build and next start. You can customize environment variables in the dashboard.
3. Deploy preview environments: Every pull request gets its own preview URL, which is great for QA and testing.
4. Production deployment: When you merge to the main branch, Vercel builds and deploys your app globally on their CDN and serverless infrastructure.

This process is straightforward and requires minimal DevOps knowledge, which is why it’s popular for startups and small teams.

Example: Deploying a Next.js app with API routes

Next.js API routes run as serverless functions on Vercel. Here’s a simple example:

export default function handler(req, res) {
  res.status(200).json({ message: 'Hello from API route!' });
}

When deployed, this code runs in a serverless environment, scaling automatically without you worrying about server management.

Deploying Next.js on Custom Servers

Sometimes you need more control or want to integrate with existing infrastructure. In those cases, you might deploy Next.js on your own Node.js server.

The typical steps are:

1. Run next build to compile your app.
2. Run next start to start the Node.js server.
3. Use a process manager like PM2 or systemd to keep the server running.
4. Set up a reverse proxy (e.g., Nginx) to handle HTTPS, load balancing, and static assets.

This approach gives you full control but requires more maintenance. You’re responsible for scaling, monitoring, and security patches.

Example: Basic server start script

npm run build
npm run start

Or with PM2:

pm2 start npm --name "next-app" -- start

Best Practices for Next.js Deployment

• Use environment variables carefully: Never expose secrets in the client bundle. Use process.env for server-only variables and NEXT_PUBLIC_ prefix for public ones.
• Optimize images: Use Next.js Image component with an appropriate loader to improve performance.
• Enable caching and CDN: Static assets and SSG pages should be served via CDN for faster load times.
• Monitor build times: Large sites can have slow builds; consider ISR or splitting your app into smaller parts.
• Automate deployments: Use CI/CD pipelines to ensure consistent builds and deployments.
• Handle fallback pages: When using ISR or dynamic routes, configure fallback behavior to avoid broken pages.

Common Mistakes Developers Make

• Confusing SSR and SSG: Deploying SSR apps as static sites leads to broken functionality.
• Not setting environment variables properly: This can cause runtime errors or expose sensitive data.
• Ignoring build errors: Sometimes builds succeed but with warnings that cause runtime issues.
• Overusing SSR: SSR can add latency and increase server costs. Use SSG or ISR when possible.
• Not testing preview deployments: Skipping preview environments leads to bugs reaching production.

Performance Considerations

Performance is often a key concern in deployment. Here’s what I focus on:

• Static generation first: If your content doesn’t change often, pre-render pages at build time to serve instantly.
• Use ISR for dynamic content: This reduces server load by regenerating pages only when needed.
• Minimize serverless cold starts: On platforms like Vercel or AWS Lambda, cold starts can add latency. Keep functions lightweight and warm if possible.
• Leverage CDN caching: Cache static assets aggressively to reduce load times globally.
• Optimize bundle size: Use dynamic imports and code splitting to reduce initial load.

Security Considerations

Security is often overlooked but crucial. Here are some tips:

• Never expose secrets in client code: Use server-side environment variables and API routes to keep secrets safe.
• Sanitize user input: If your app accepts input, validate and sanitize it to prevent injection attacks.
• Use HTTPS: Always serve your app over HTTPS to protect data in transit.
• Set appropriate HTTP headers: Use Content Security Policy (CSP), X-Frame-Options, and other headers to harden your app.
• Keep dependencies updated: Regularly update Next.js and related packages to patch vulnerabilities.

Interview Tips for Next.js Deployment Questions

• Explain your reasoning: Interviewers want to hear why you choose a particular deployment method, not just what you did.
• Discuss trade-offs: Mention the pros and cons of SSR vs SSG vs ISR and how they affect deployment.
• Bring up real-world constraints: Talk about cost, team expertise, and infrastructure requirements.
• Show awareness of platform features: If you mention Vercel or Netlify, highlight their unique benefits and limitations.
• Be ready to talk about troubleshooting: Common deployment issues like environment variable misconfigurations or build failures come up often.

Practical Production Scenarios

Here are a few scenarios I’ve encountered and how I handled deployment:

Scenario 1: Marketing site with mostly static content

We used Next.js static export (next export) and deployed to Netlify. This gave us fast load times and simple hosting without a Node.js server. We set up redirects and headers in Netlify config to handle SEO and caching.

Scenario 2: E-commerce site with dynamic product pages

We used ISR to pre-render product pages and regenerate them when inventory changed. Deployed on Vercel to take advantage of serverless functions for API routes and edge caching. This balanced performance and freshness.

Scenario 3: Internal dashboard with authentication

We deployed on a custom AWS EC2 instance with a Node.js server. This allowed us to integrate with internal APIs securely and control deployment pipelines tightly. We used PM2 for process management and Nginx for SSL termination.

Comparing Next.js Deployment Alternatives

Deployment Type	Use Case	Pros	Cons
Static Export (SSG)	Content that rarely changes	Fast, cheap, easy to scale	Not suitable for dynamic content
Server-Side Rendering (SSR)	Highly dynamic content	Always fresh data	Higher latency, more server resources
Incremental Static Regeneration (ISR)	Mostly static with some dynamic updates	Good balance of speed and freshness	Complexity in cache invalidation
Hybrid (SSR + SSG + ISR)	Complex apps with mixed needs	Flexible, optimized per page	Requires careful planning

Choosing the right deployment approach depends on your app’s requirements and constraints. I always recommend starting with the simplest model that meets your needs and evolving as complexity grows.