Expo API Routes

Build API routes and server functions with Expo for full-stack mobile development

Category: development Source: expo/skills

Expo API Routes is a development skill for building server-side API endpoints and backend functions directly within Expo projects, covering full-stack mobile development, request handling, and serverless function deployment

What Is This?

Overview

Expo API Routes enables developers to create backend API endpoints without leaving the Expo ecosystem. Instead of managing separate backend servers, you can define API routes that handle HTTP requests, database operations, and business logic alongside your mobile application code. This approach streamlines full-stack development by keeping frontend and backend code in a single project structure, reducing the need for context switching and simplifying code management.

The skill leverages Expo's infrastructure to provide serverless function capabilities, allowing you to deploy API endpoints that scale automatically. You write simple JavaScript functions that respond to HTTP requests, and Expo handles the deployment, routing, and infrastructure management behind the scenes. This means you can focus on writing business logic and application features rather than worrying about server provisioning, scaling, or security patches.

API routes are typically placed in a designated directory (such as /api) within your Expo project. Each file in this directory corresponds to a unique endpoint, and the exported handler function processes incoming requests. Expo’s tooling ensures that these routes are bundled and deployed efficiently, making it easy to iterate on both frontend and backend features together.

Who Should Use This

Mobile developers building full-stack applications with Expo who want to avoid managing separate backend infrastructure. Teams seeking faster development cycles by keeping API and mobile code together. Developers new to backend development who prefer a simplified serverless approach. This skill is also valuable for solo developers or small teams who want to minimize operational overhead and focus on delivering features quickly.

Why Use It?

Problems It Solves

Managing separate backend servers adds complexity and operational overhead to mobile projects. Expo API Routes eliminates this by providing built-in serverless functions that scale automatically without infrastructure management. You avoid context switching between frontend and backend codebases, reducing development friction and deployment complexity. This approach also reduces the risk of configuration drift and version mismatches between separate repositories.

Core Highlights

API Routes integrate seamlessly with Expo's build and deployment pipeline for unified project management. Serverless functions scale automatically based on demand without manual server configuration or maintenance. Request handling includes built-in support for HTTP methods, headers, query parameters, and request bodies. Environment variables and secrets management are handled securely through Expo's configuration system, ensuring sensitive data is protected and easily managed across environments.

How to Use It?

Basic Usage

To define an API route, create a file in your /api directory and export a handler function:

export default function handler(req, res) {
  if (req.method === 'POST') {
    const { name } = req.body;
    res.status(200).json({ message: `Hello ${name}` });
  } else {
    res.status(405).end();
  }
}

This example demonstrates handling a POST request and sending a JSON response. The handler receives the request and response objects, similar to popular Node.js frameworks.

Real-World Examples

Create a user registration endpoint that validates input and stores data:

export default async function handler(req, res) {
  if (req.method === 'POST') {
    const { email, password } = req.body;
    // Input validation and hashing would occur here
    const user = await db.users.create({ email, password });
    res.status(201).json({ userId: user.id });
  }
}

Build a data retrieval endpoint that filters results based on query parameters:

export default async function handler(req, res) {
  const { category, limit } = req.query;
  const items = await db.items.find({ category }).limit(limit);
  res.status(200).json(items);
}

You can also implement endpoints for authentication, notifications, or integrating with third-party APIs.

Advanced Tips

Use middleware patterns to handle authentication, logging, and error handling across multiple routes consistently. Leverage environment variables to manage database connections, API keys, and configuration settings separately for development and production environments. Consider using TypeScript for type safety and better developer experience. Implement input validation libraries to ensure data integrity and prevent security vulnerabilities.

When to Use It?

Use Cases

Building mobile applications that need backend functionality without managing separate server infrastructure. Creating real-time data synchronization between mobile clients and a centralized backend. Implementing authentication and authorization logic that validates requests before processing. Handling file uploads, image processing, or other resource-intensive operations server-side. Prototyping new features quickly or building minimum viable products (MVPs) with minimal setup.