Route Handlers and Middleware are the server-side pillars of the App Router. Route Handlers allow you to create custom API endpoints within your app/ directory using the route.ts file convention. Middleware runs at the Edge before a request is processed, enabling authentication checks, redirects, URL rewrites, and more. Together, they give you full control over the server-side behavior of your application.

Modern full-stack applications need more than just page rendering. You need:

• API endpoints to serve data to client components, mobile apps, or third-party services
• Authentication checks that run before protected pages load
• Request modification (redirects, rewrites, headers) at the edge
• Dynamic API behavior based on route parameters and HTTP methods
• Geolocation and A/B testing based on request metadata

Route Handlers and Middleware provide these capabilities within the App Router architecture.

By the end of this module, you will be able to:

• Create Route Handlers using the route.ts file convention
• Handle different HTTP methods (GET, POST, PUT, PATCH, DELETE)
• Access dynamic route parameters in API routes
• Implement middleware for authentication and redirects
• Configure middleware matching for specific routes
• Use middleware for A/B testing, geolocation, and request modification

• Completed Module 1 and Module 2 of Phase 2
• Understanding of HTTP methods and REST API concepts
• Basic knowledge of request/response patterns
• Familiarity with dynamic routes

1. What are Route Handlers?
2. HTTP Methods & Dynamic Routes in Route Handlers
3. Middleware Basics
4. Advanced Middleware Patterns

• Route Handler file convention (route.ts)
• Supported HTTP methods: GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS
• Request body parsing (JSON, FormData)
• Response patterns (JSON, redirect, streaming)
• Dynamic route parameters in Route Handlers
• Middleware file location and structure
• Middleware matcher configuration
• Authentication checks in middleware
• Redirect and rewrite patterns
• Geolocation, cookies, and headers in middleware
• Edge runtime considerations

12-15 hours to complete all topics and exercises.

• Building a REST API for client components
• Creating webhook endpoints for third-party services
• Implementing authentication guards at the edge
• Setting up internationalization redirects
• Running A/B tests with middleware-based routing
• Building rate-limiting and bot protection

• Build a CRUD API for a resource (e.g., todos, products)
• Implement auth middleware for protected routes
• Create a geolocation-based redirect system
• Build a webhook handler with signature verification

• REST API Backend: Build a complete REST API with CRUD operations, validation, and error handling
• Auth System: Implement middleware-based authentication with route protection and redirects

• Data Fetching (Phase 3)
• Authentication (Phase 5)
• Server Actions (Phase 4)
• Edge Runtime