NestJS vs Express vs Fastify comparison - Hands-On Comparison

Build a Simple API with NestJS, Express, and Fastify

📖 Scenario: You are creating a simple API to manage a list of books for a small library. You want to understand how to set up this API using three popular Node.js frameworks: NestJS, Express, and Fastify. This will help you see the differences in setup and structure.

🎯 Goal: Build a basic API endpoint /books that returns a list of books using NestJS, Express, and Fastify. You will create the data, configure the server, implement the route, and complete the setup for each framework.

📋 What You'll Learn

Create a list of books with exact titles and authors

Set up a configuration variable for the server port

Implement a GET route /books that returns the book list

Complete the server start code for each framework

💡 Why This Matters

🌍 Real World

APIs like this are common in web apps to provide data to frontend clients or other services.

💼 Career

Understanding how to set up routes and servers in popular Node.js frameworks is essential for backend development roles.

1

Create the books data list

Create a constant array called books with these exact objects: { title: 'The Hobbit', author: 'J.R.R. Tolkien' }, { title: '1984', author: 'George Orwell' }, and { title: 'To Kill a Mockingbird', author: 'Harper Lee' }.

NestJS

// Create the books array with exact objects
// Your code here

Hint

Use const books = [ ... ] with objects inside.

2

Set the server port configuration

Create a constant called PORT and set it to 3000.

NestJS

const books = [
  { title: 'The Hobbit', author: 'J.R.R. Tolkien' },
  { title: '1984', author: 'George Orwell' },
  { title: 'To Kill a Mockingbird', author: 'Harper Lee' }
];

// Create a constant PORT and set it to 3000
// Your code here

Hint

Use const PORT = 3000; to set the port number.

3

Implement the GET /books route

Use app.get('/books', (req, res) => { res.json(books); }) to create a route that returns the books array as JSON.

NestJS

const books = [
  { title: 'The Hobbit', author: 'J.R.R. Tolkien' },
  { title: '1984', author: 'George Orwell' },
  { title: 'To Kill a Mockingbird', author: 'Harper Lee' }
];

const PORT = 3000;

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

// Add a GET route for '/books' that returns the books array as JSON
// Your code here

Hint

Use app.get('/books', (req, res) => { res.json(books); }).

4

Start the server listening on the port

Add app.listen(PORT, () => { console.log(`Server running on port ${PORT}`); }); to start the Express server.

NestJS

const books = [
  { title: 'The Hobbit', author: 'J.R.R. Tolkien' },
  { title: '1984', author: 'George Orwell' },
  { title: 'To Kill a Mockingbird', author: 'Harper Lee' }
];

const PORT = 3000;

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

app.get('/books', (req, res) => {
  res.json(books);
});

// Start the server listening on PORT
// Your code here

Hint

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

Practice

1. Which framework is known for providing a structured architecture with decorators and dependency injection?

easy

A. Fastify

B. Express

C. NestJS

D. Koa

Solution

1. Step 1: Understand framework features

   NestJS is designed with a modular architecture, using decorators and dependency injection to organize code clearly.

2. Step 2: Compare with other frameworks

   Express is minimal and flexible but lacks built-in structure; Fastify focuses on speed but not on architectural patterns.

3. Final Answer:

   NestJS -> Option C

4. Quick Check:

   Structured framework = NestJS [OK]

Hint: Structured + decorators = NestJS [OK]

Common Mistakes:

• Confusing Express's flexibility with structure
• Thinking Fastify has built-in dependency injection
• Choosing Koa which is unrelated here

2. Which of the following is the correct way to create a Fastify server instance?

easy

A. const app = fastify();

B. const app = express();

C. const app = new NestFactory();

D. const app = new Koa();

Solution

1. Step 1: Recall Fastify server creation syntax

   Fastify servers are created by calling the fastify() function, not using new keyword.

2. Step 2: Eliminate other options

   Express uses express(), NestJS uses NestFactory.create(), and Koa uses new Koa().

3. Final Answer:

   const app = fastify(); -> Option A

4. Quick Check:

   Fastify instance = fastify() [OK]

Hint: Fastify uses fastify() function call [OK]

Common Mistakes:

• Using new keyword with fastify
• Confusing Express and Fastify syntax
• Using NestFactory directly for Fastify

3. Given the following code snippet, what will be the main difference in performance between NestJS using Express and Fastify?

const app = await NestFactory.create(AppModule, { logger: true });
await app.listen(3000);

medium

A. NestJS with Express is faster due to simpler middleware

B. NestJS with Fastify is faster due to optimized HTTP handling

C. Both have identical performance because NestJS abstracts the server

D. NestJS with Express supports HTTP/2 by default, Fastify does not

Solution

1. Step 1: Understand NestJS adapters

   NestJS can use Express or Fastify under the hood. Fastify is designed for speed and efficiency.

2. Step 2: Compare performance traits

   Fastify has optimized HTTP handling and lower overhead, making it faster than Express in most cases.

3. Final Answer:

   NestJS with Fastify is faster due to optimized HTTP handling -> Option B

4. Quick Check:

   Fastify = faster HTTP handling [OK]

Hint: Fastify is faster than Express in NestJS [OK]

Common Mistakes:

• Assuming Express is faster due to simplicity
• Thinking NestJS removes all performance differences
• Confusing HTTP/2 support defaults

4. You wrote a NestJS app using Fastify adapter but get an error: TypeError: app.listen is not a function. What is the most likely cause?

medium

A. You forgot to import FastifyModule in AppModule

B. Fastify does not support listen method

C. You called app.listen before await

D. You did not use NestFactory.create with Fastify adapter

Solution

1. Step 1: Check how NestJS app is created with Fastify

   To use Fastify, you must pass the Fastify adapter to NestFactory.create().

2. Step 2: Understand error cause

   If you skip the adapter, NestJS defaults to Express, but if you mix Fastify code without adapter, app.listen may be undefined.

3. Final Answer:

   You did not use NestFactory.create with Fastify adapter -> Option D

4. Quick Check:

   Fastify adapter required for app.listen [OK]

Hint: Use Fastify adapter in NestFactory.create [OK]

Common Mistakes:

• Assuming FastifyModule import is enough
• Calling listen without await causes different error
• Thinking Fastify lacks listen method

5. You want to build a high-performance REST API with automatic validation, modular structure, and fast response times. Which combination best fits this requirement?

hard

A. NestJS using Fastify adapter with class-validator and modules

B. Fastify with no framework on top

C. NestJS using Express adapter without validation

D. Express with manual middleware and no structure

Solution

1. Step 1: Identify requirements

   High performance, automatic validation, and modular structure require a framework with features and speed.

2. Step 2: Match frameworks to needs

   Express alone lacks structure and automatic validation; Fastify alone lacks modularity; NestJS provides structure and validation, and Fastify adapter adds speed.

3. Final Answer:

   NestJS using Fastify adapter with class-validator and modules -> Option A

4. Quick Check:

   Structure + validation + speed = NestJS + Fastify [OK]

Hint: Combine NestJS structure + Fastify speed + validation [OK]

Common Mistakes:

• Choosing Express for automatic validation
• Ignoring modularity in Fastify alone
• Using NestJS with Express loses speed advantage