Edge runtime vs Node.js runtime in NextJS - When to Use Which

The Big Idea

Discover how running code closer to users can make your website feel instant!

The Scenario

Imagine you have a website that needs to respond quickly to users all over the world. You try to run your code on a single server far away from many users.

Every time someone visits, the server takes time to process and send back the response.

The Problem

Using only a traditional Node.js server means requests from distant users travel far, causing delays.

Also, Node.js servers can be heavy and slower to start, making your site feel sluggish.

The Solution

Edge runtimes run your code closer to users, at many locations worldwide, making responses faster.

They start quickly and handle simple tasks efficiently, improving user experience.

Before vs After

✗ Before

app.listen(3000, () => console.log('Server running'))

✓ After

export const runtime = 'edge';
export default function handler(req) { return new Response('Fast response'); }

What It Enables

It enables lightning-fast responses by running code near users, improving speed and scalability.

Real Life Example

A global news site uses edge runtime to deliver breaking news instantly to readers everywhere without delay.

Key Takeaways

Node.js runs on central servers, which can slow down distant users.

Edge runtime runs code near users, speeding up responses.

Choosing the right runtime improves website speed and user happiness.

Practice

1. What is the main advantage of using the Edge runtime in Next.js?

easy

A. It runs code closer to users for faster response times.

B. It supports all Node.js modules without restrictions.

C. It allows using server-side rendering only on the server.

D. It automatically caches all API responses indefinitely.

Solution

1. Step 1: Understand Edge runtime purpose

   The Edge runtime runs code on servers geographically closer to users, reducing latency.

2. Step 2: Compare with Node.js runtime

   Unlike Node.js runtime, Edge runtime focuses on speed by running near users but has some limitations on Node features.

3. Final Answer:

   It runs code closer to users for faster response times. -> Option A

4. Quick Check:

   Edge runtime = faster user response [OK]

Hint: Edge runtime means code runs near users for speed [OK]

Common Mistakes:

• Thinking Edge runtime supports all Node.js modules
• Confusing Edge runtime with full Node.js capabilities
• Assuming Edge runtime caches all responses automatically

2. Which is the correct way to set the runtime to Edge in a Next.js API route?

easy

A. export const runtime = 'nodejs';

B. const runtime = 'edge';

C. export default runtime = 'edge';

D. export const runtime = 'edge';

Solution

1. Step 1: Recall syntax for setting runtime

   Next.js requires exporting a constant named runtime with value 'edge' or 'nodejs'.

2. Step 2: Identify correct export statement

   The correct syntax is export const runtime = 'edge'; to set Edge runtime.

3. Final Answer:

   export const runtime = 'edge'; -> Option D

4. Quick Check:

   Use export const runtime = 'edge' [OK]

Hint: Use export const runtime = 'edge' to set Edge runtime [OK]

Common Mistakes:

• Using default export instead of named export
• Assigning runtime without export
• Setting runtime to 'nodejs' when Edge is needed

3. Given this Next.js API route code, what will be the runtime environment if export const runtime = 'edge'; is set?

export const runtime = 'edge';
export default function handler(req) {
  return new Response('Hello from Edge!');
}

medium

A. Node.js runtime with full Node APIs

B. Edge runtime with limited Node APIs

C. Client-side runtime in the browser

D. Serverless function with no runtime

Solution

1. Step 1: Check the runtime export

   The code explicitly sets runtime = 'edge', so it uses the Edge runtime environment.

2. Step 2: Understand Edge runtime features

   Edge runtime supports limited Node.js APIs and runs close to users for speed, unlike full Node.js runtime.

3. Final Answer:

   Edge runtime with limited Node APIs -> Option B

4. Quick Check:

   runtime = 'edge' means Edge runtime [OK]

Hint: runtime = 'edge' means limited Node APIs near users [OK]

Common Mistakes:

• Assuming full Node.js APIs are available in Edge runtime
• Confusing Edge runtime with client-side code
• Thinking no runtime is used

4. Identify the error in this Next.js API route code intended to run on Edge runtime:

export const runtime = 'edge';
import fs from 'fs';
export default function handler(req) {
  const data = fs.readFileSync('/data.txt', 'utf8');
  return new Response(data);
}

medium

A. Edge runtime does not support importing 'fs' module.

B. Missing async keyword for handler function.

C. Response constructor is used incorrectly.

D. The runtime should be set to 'nodejs' instead.

Solution

1. Step 1: Check module usage in Edge runtime

   Edge runtime does not support Node.js built-in modules like 'fs' because it runs in a restricted environment.

2. Step 2: Identify the error cause

   Importing and using 'fs' causes a runtime error in Edge runtime; this is not allowed.

3. Final Answer:

   Edge runtime does not support importing 'fs' module. -> Option A

4. Quick Check:

   Edge runtime forbids 'fs' module [OK]

Hint: Edge runtime forbids Node built-in modules like fs [OK]

Common Mistakes:

• Thinking async is required here
• Believing Response usage is wrong
• Assuming runtime setting is incorrect

5. You want to create a Next.js API route that uses crypto for hashing and runs as close to users as possible. Which runtime should you choose and why?

hard

A. Node.js runtime, because it supports all Node modules including crypto.

B. Node.js runtime, because Edge runtime does not support any crypto functions.

C. Edge runtime, because it supports Web Crypto API and runs near users.

D. Edge runtime, but you must polyfill crypto manually.

Solution

1. Step 1: Understand crypto support in runtimes

   Edge runtime supports the Web Crypto API natively, which can be used for hashing, while Node.js runtime supports Node's crypto module.

2. Step 2: Choose runtime for proximity and crypto

   Since you want to run close to users and use crypto, Edge runtime is best because it supports Web Crypto and runs near users.

3. Final Answer:

   Edge runtime, because it supports Web Crypto API and runs near users. -> Option C

4. Quick Check:

   Edge runtime + Web Crypto API = best choice [OK]

Hint: Edge runtime supports Web Crypto API and is faster globally [OK]

Common Mistakes:

• Assuming Edge runtime lacks any crypto support
• Choosing Node.js runtime despite wanting low latency
• Thinking manual polyfill is needed for crypto in Edge