Vercel deployment (default) in NextJS - Performance & Optimization

Performance: Vercel deployment (default)

MEDIUM IMPACT

This affects the initial page load speed and runtime performance by how the Next.js app is built, cached, and served on Vercel's edge network.

Deploying a Next.js app on Vercel with default settings

NextJS

next build && vercel --prod
// Use Incremental Static Regeneration (ISR) or static export for pages
// Configure caching headers in next.config.js

Pages are served from edge cache or pre-built static files, reducing serverless cold starts and speeding up response.

📈 Performance Gainreduces LCP by 100-300ms, fewer serverless invocations

Deploying a Next.js app on Vercel with default settings

NextJS

next build && vercel --prod
// No custom caching or ISR configured, all pages are server-rendered on demand

Every page request triggers a serverless function cold start causing slower response times and higher latency.

📉 Performance Costblocks rendering for 200-500ms on cold start, increases LCP

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Default SSR on Vercel	Minimal DOM nodes (depends on app)	1 reflow per page load	Moderate paint cost	[! ] OK
Static Generation or ISR	Minimal DOM nodes	1 reflow per page load	Low paint cost	[OK] Good

Rendering Pipeline

When a user requests a page, Vercel routes it to the nearest edge location. If the page is static or cached, it is served immediately. If server-side rendering is needed, a serverless function runs, generating HTML before sending it to the browser.

→Server-side Rendering

→Network Transfer

→Browser Rendering

⚠️ BottleneckServerless function cold start latency during SSR

Core Web Vital Affected

LCP

This affects the initial page load speed and runtime performance by how the Next.js app is built, cached, and served on Vercel's edge network.

Optimization Tips

1Use static generation or ISR to reduce serverless cold start delays.

2Configure caching headers to leverage Vercel's edge network.

3Monitor TTFB in DevTools to detect server-side latency issues.

Performance Quiz - 3 Questions

What is a common cause of slower page loads on default Vercel deployments using SSR?

A Serverless function cold starts causing delayed HTML generation

B Too many DOM nodes causing layout thrashing

C Large CSS files blocking rendering

D Client-side JavaScript errors

DevTools: Performance

How to check: Open Chrome DevTools > Performance tab > Record page load > Look for long server response times and scripting delays

What to look for: High Time to First Byte (TTFB) and long scripting blocks indicate serverless cold starts affecting LCP

Practice

1. What is the main purpose of deploying a Next.js app on Vercel using the default settings?

easy

A. To create a backup of your app files

B. To run the app only on your local machine

C. To convert the app into a mobile application

D. To make the app live on the internet with minimal setup

Solution

1. Step 1: Understand Vercel deployment purpose

   Vercel deployment is designed to host your Next.js app online so others can access it.

2. Step 2: Recognize default deployment behavior

   Using default settings, Vercel automatically builds and hosts your app live on the internet.

3. Final Answer:

   To make the app live on the internet with minimal setup -> Option D

4. Quick Check:

   Vercel deployment = live app hosting [OK]

Hint: Vercel default deploy means live app online quickly [OK]

Common Mistakes:

• Thinking deployment only runs locally
• Confusing deployment with app backup
• Assuming deployment converts app to mobile

2. Which command correctly deploys a Next.js app to Vercel using the CLI with default settings?

easy

A. vercel deploy --prod

B. vercel

C. vercel --prod

D. deploy vercel

Solution

1. Step 1: Recall Vercel CLI default deploy command

   The basic command to deploy is simply vercel, which starts the deployment process.

2. Step 2: Understand optional flags

   While --prod deploys to production, the default deploy command without flags is just vercel.

3. Final Answer:

   vercel -> Option B

4. Quick Check:

   Default deploy command = vercel [OK]

Hint: Use just 'vercel' to deploy with defaults [OK]

Common Mistakes:

• Adding unnecessary flags like --prod by default
• Using wrong command order like 'deploy vercel'
• Confusing 'vercel --prod' as default

3. After running vercel to deploy your Next.js app, what will you see in the terminal if the deployment is successful?

medium

A. A URL link where your app is live

B. An error message about missing files

C. A prompt to install Next.js

D. A message saying deployment is disabled

Solution

1. Step 1: Understand Vercel deployment output

   When deployment succeeds, Vercel shows a URL link to access your live app.

2. Step 2: Identify success vs error messages

   Error messages or prompts indicate failure or missing setup, not success.

3. Final Answer:

   A URL link where your app is live -> Option A

4. Quick Check:

   Successful deploy shows live app URL [OK]

Hint: Look for live URL in terminal after deploy [OK]

Common Mistakes:

• Expecting no output after deploy
• Confusing error messages as success
• Thinking deployment disables app

4. You ran vercel but your app fails to deploy with a build error. What is the most likely cause?

medium

A. Your internet connection is too fast

B. You forgot to install Vercel CLI globally

C. Missing package.json or build scripts in your project

D. You used the wrong terminal emulator

Solution

1. Step 1: Identify build error causes in Vercel

   Build errors usually happen if essential files like package.json or build scripts are missing.

2. Step 2: Rule out unrelated causes

   Not installing CLI prevents running commands, but here command ran. Internet speed or terminal choice doesn't cause build errors.

3. Final Answer:

   Missing package.json or build scripts in your project -> Option C

4. Quick Check:

   Build error = missing config files [OK]

Hint: Check package.json and build scripts if build fails [OK]

Common Mistakes:

• Blaming internet speed for build errors
• Assuming CLI install issues cause build errors
• Thinking terminal type affects build

5. You want to deploy a Next.js app on Vercel with default settings but exclude a folder named tests from the deployment. How can you achieve this?

hard

A. Add tests/ to a .vercelignore file in your project root

B. Rename the folder to _tests so Vercel ignores it automatically

C. Delete the tests folder before deploying

D. Use a CLI flag --ignore tests when running vercel

Solution

1. Step 1: Understand how to exclude files/folders in Vercel

   Vercel supports a .vercelignore file to specify files or folders to skip during deployment.

2. Step 2: Apply exclusion for the tests folder

   Adding tests/ line in .vercelignore tells Vercel to ignore that folder automatically.

3. Final Answer:

   Add tests/ to a .vercelignore file in your project root -> Option A

4. Quick Check:

   Use .vercelignore to exclude folders [OK]

Hint: Use .vercelignore file to exclude folders [OK]

Common Mistakes:

• Renaming folders expecting auto-ignore
• Deleting folders instead of ignoring
• Using non-existent CLI flags to ignore