NestJS vs. Fastify: Which One is Better for High-Performance APIs?

In the previous article, we learned about the exciting developments in React 19’s server components and how they promise to revolutionize frontend development. As frontend technologies like these evolve, the backend systems powering them must rise to the challenge, delivering APIs that are fast, scalable, and seamlessly integrated. This is where NestJS and Fastify come into play—two leading Node.js frameworks designed for building high-performance APIs.

In the world of Node.js development, choosing the right framework for building high-performance APIs can make or break your project. Two frameworks that frequently come up in this discussion are NestJS and Fastify. Both are powerful tools in the Node.js ecosystem, but they cater to different needs and priorities. Whether you’re aiming for raw speed, scalability, or a robust developer experience, this in-depth guide will compare NestJS and Fastify across performance, use cases, developer experience, and more. By the end, you’ll have a clear understanding of which framework—or combination—best suits your high-performance API needs.

Introduction

Building a high-performance API requires balancing speed, scalability, and maintainability. NestJS and Fastify are two popular frameworks that address these needs in unique ways:

• NestJS is a TypeScript-based framework inspired by Angular, designed for building scalable, maintainable server-side applications. It uses Express by default but can switch to Fastify for enhanced performance.
• Fastify is a lightweight, performance-focused web framework that prioritizes speed and efficiency with a minimalist API and a powerful plugin system.

The debate over “NestJS vs. Fastify” often centers on project requirements: Do you need a structured, feature-rich framework, or a lean, blazing-fast solution? This guide will explore both frameworks in depth, comparing their features, performance metrics, and real-world applications. We’ll also look at a hybrid approach—using NestJS with Fastify—to see if it offers the best of both worlds.

Overview of NestJS

What is NestJS?

NestJS is a progressive Node.js framework that simplifies the creation of efficient, reliable, and scalable applications. Built with TypeScript, it combines object-oriented programming (OOP), functional programming (FP), and functional reactive programming (FRP). By default, NestJS uses Express as its HTTP server, but its platform-agnostic design allows it to integrate with other frameworks like Fastify.

NestJS shines in scenarios where architecture and maintainability are critical. Its modular design and built-in features make it a favorite for enterprise-grade applications.

Key Features of NestJS

• Modular Architecture: Organize your code into reusable modules for better scalability and maintainability.
• Dependency Injection: A built-in system inspired by Angular, making dependency management and testing easier.
• TypeScript Native: Offers type safety and modern JavaScript features out of the box.
• Middleware and Interceptors: Add custom logic to the request-response lifecycle with ease.
• Multi-Transport Support: Build REST APIs, GraphQL servers, WebSockets, or microservices within the same framework.

Configuring NestJS with Fastify

While NestJS defaults to Express, you can swap it for Fastify to boost performance. Here’s how to set it up:

import { NestFactory } from '@nestjs/core';
import { FastifyAdapter, NestFastifyApplication } from '@nestjs/platform-fastify';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create<NestFastifyApplication>(
    AppModule,
    new FastifyAdapter(),
  );
  await app.listen(3000, '0.0.0.0');
}
bootstrap();

Install the required package first:

npm install @nestjs/platform-fastify

This configuration lets NestJS leverage Fastify’s speed while retaining its architectural benefits. We’ll explore the performance impact later.

For more details, check the official NestJS documentation.

Overview of Fastify

What is Fastify?

Fastify is a high-performance web framework for Node.js, designed to deliver exceptional speed with minimal overhead. It’s built from the ground up to be one of the fastest frameworks in the ecosystem, making it ideal for performance-critical APIs. Fastify’s lightweight core and plugin system allow developers to extend functionality without sacrificing efficiency.

Key Features of Fastify

• Blazing Fast: Optimized for high requests-per-second (RPS) and low latency.
• Lightweight Design: Minimal overhead ensures efficient resource use.
• Plugin System: Extend functionality with a modular, reusable plugin architecture.
• Schema Validation: Built-in JSON schema support for faster serialization and validation.
• Express-Like Simplicity: Easy to learn for developers familiar with Express.

Here’s a basic Fastify setup:

const fastify = require('fastify')({ logger: true });

fastify.get('/', async (request, reply) => {
  return { message: 'Hello, Fastify!' };
});

fastify.listen({ port: 3000 }, (err) => {
  if (err) throw err;
  console.log('Server running on port 3000');
});

Install Fastify with:

npm install fastify

Learn more at the Fastify documentation.

Performance Comparison

Performance is often the deciding factor for high-performance APIs. Let’s break down how NestJS and Fastify stack up.

Benchmarks

Benchmarks provide a snapshot of raw performance. Here’s what studies and community tests reveal:

• Requests per Second (RPS):
• Fastify: Up to 50,000+ RPS for simple endpoints (e.g., “Hello World”).
• NestJS with Express: Around 15,000–20,000 RPS.
• NestJS with Fastify: Approaches 40,000–50,000 RPS, closing the gap with standalone Fastify.
• Latency: Fastify consistently shows lower latency (faster response times) than Express-based NestJS.
• Memory Usage: Fastify uses less memory due to its lightweight design, while NestJS (especially with Express) has a slightly higher footprint.

For example, in a benchmark by NearForm, Fastify outperformed Express by a significant margin. When NestJS adopts Fastify as its adapter, it inherits much of this performance boost.

Real-World Scenarios

Benchmarks are useful, but real-world applications involve more complexity:

• CPU-Intensive Tasks: Fastify excels in tasks like JWT verification or data parsing due to its optimized core. NestJS with Express lags here, but the Fastify adapter narrows the gap.
• Database-Heavy Apps: When APIs rely on database queries (e.g., PostgreSQL or MongoDB), the framework’s performance becomes less impactful than the database’s efficiency.
• High Concurrency: Fastify handles high traffic with ease, making it ideal for public-facing APIs. NestJS performs well too, especially with Fastify, but its overhead can be noticeable under extreme loads.

NestJS with Fastify: The Hybrid Advantage

Switching NestJS to the Fastify adapter significantly improves its performance. For instance, a simple API endpoint might see RPS jump from 17,000 (Express) to 45,000 (Fastify adapter). This hybrid approach combines NestJS’s structure with Fastify’s speed, offering a compelling option for performance-critical projects.

Use Cases

The right framework depends on your project’s goals. Here’s when each shines—and how a hybrid approach fits in.

When to Choose NestJS

• Complex Applications: NestJS’s modular architecture is perfect for large-scale apps with multiple features, like e-commerce platforms or enterprise dashboards.
• Enterprise Needs: Its opinionated structure, TypeScript support, and dependency injection suit teams building reliable, long-term projects.
• Multi-Transport Apps: Need REST, GraphQL, and WebSockets in one app? NestJS handles it seamlessly.
• Angular Teams: Developers familiar with Angular will adapt quickly to NestJS’s similar patterns.

Example: A corporate CRM system with REST APIs, real-time notifications via WebSockets, and a GraphQL layer for analytics.

When to Choose Fastify

• High-Performance APIs: For APIs needing maximum throughput (e.g., IoT backends or real-time analytics), Fastify’s speed is unmatched.
• Lightweight Projects: Small to medium-sized apps benefit from Fastify’s minimalism and simplicity.
• Extensible Systems: The plugin system makes it easy to add features like authentication or caching.
• Quick Prototypes: Fastify’s shallow learning curve speeds up development for MVPs.

Example: A public API serving thousands of requests per second with minimal latency, like a weather service.

NestJS with Fastify: Best of Both Worlds

• Performance + Structure: Use this combo for apps needing NestJS’s architecture and Fastify’s speed, such as a scalable SaaS platform with high traffic.
• Gradual Scaling: Start with Fastify’s simplicity, then adopt NestJS’s structure as the project grows.

Example: A startup’s API that begins as a simple service but evolves into a feature-rich platform.

Developer Experience

Beyond performance, the developer experience—ease of use, learning curve, and community support—matters.

Ease of Use and Learning Curve

• NestJS: Steeper learning curve due to TypeScript, decorators, and dependency injection. However, Angular developers will feel at home. The payoff is a structured, maintainable codebase.
• Fastify: Simpler and more approachable, especially for Express users. Its minimal API means less to learn upfront.

Community and Documentation

• NestJS: Boasts a large, active community with comprehensive documentation, tutorials, and third-party resources. GitHub stars: ~60k+.
• Fastify: Smaller but growing community (GitHub stars: ~30k+). Documentation is solid, though fewer external resources exist compared to NestJS.

Middleware and Plugins

• NestJS: Leverages Express’s vast middleware ecosystem by default. With Fastify, it taps into a smaller but high-quality plugin pool.
• Fastify: Its plugin system is a standout, offering modular extensions like @fastify/jwt or @fastify/cors. Fewer options than Express, but performance-focused.

Practical Examples

Let’s see both frameworks in action with a simple API endpoint.

NestJS Example (with Fastify Adapter)

Create a basic NestJS app:

npm i -g @nestjs/cli
nest new nest-api
cd nest-api
npm install @nestjs/platform-fastify

Update main.ts:

import { NestFactory } from '@nestjs/core';
import { FastifyAdapter, NestFastifyApplication } from '@nestjs/platform-fastify';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create<NestFastifyApplication>(
    AppModule,
    new FastifyAdapter(),
  );
  await app.listen(3000);
}
bootstrap();

Add a controller (src/app.controller.ts):

import { Controller, Get } from '@nestjs/common';

@Controller()
export class AppController {
  @Get()
  getHello(): string {
    return 'Hello from NestJS with Fastify!';
  }
}

Run it:

npm run start

Fastify Example

Set up a Fastify app:

npm init -y
npm install fastify

Create index.js:

const fastify = require('fastify')({ logger: true });

fastify.get('/', async (request, reply) => {
  reply.send({ message: 'Hello from Fastify!' });
});

fastify.listen({ port: 3000 }, (err) => {
  if (err) throw err;
  console.log('Server running on port 3000');
});

Run it:

node index.js

Both examples are simple, but NestJS offers more structure for complex apps, while Fastify keeps things lean and fast.

Conclusion

So, NestJS vs. Fastify: which one is better for high-performance APIs? It depends on your priorities:

• Choose NestJS for complex, scalable applications where structure and versatility matter most. It’s ideal for enterprise projects or teams leveraging TypeScript and Angular-like patterns.
• Choose Fastify for raw speed and simplicity, perfect for lightweight, high-throughput APIs or quick prototypes.
• Choose NestJS with Fastify for a hybrid solution that balances performance and architecture—a great fit for growing projects needing both.

Recommendations

• Small, Performance-Critical Projects: Go with standalone Fastify.
• Large, Feature-Rich Applications: Opt for NestJS with the Fastify adapter for performance gains.
• Unsure? Experiment!: Start with Fastify for simplicity, then scale to NestJS if needed.

Explore both frameworks yourself:

• NestJS Official Docs
• Fastify Official Docs