What is Middleware?

Middleware in Frontend Accelerator runs at the edge (on CDN nodes worldwide) before requests reach your application, providing ultra-fast authentication checks and request preprocessing.

Location:

// middleware.ts (root of project)
export { default } from 'next-auth/middleware';

export const config = {
  matcher: ['/dashboard/:path*', '/api/protected/:path*']
};

Common Use Cases:

1. Authentication Protection:

import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';

export function middleware(request: NextRequest) {
  const token = request.cookies.get('next-auth.session-token');
  
  if (!token && request.nextUrl.pathname.startsWith('/dashboard')) {
    return NextResponse.redirect(new URL('/login', request.url));
  }
  
  return NextResponse.next();
}

2. Role-Based Access:

• Check user roles before page access
• Redirect unauthorized users
• Add custom headers based on user permissions

3. Request Modifications:

• Rewrite URLs for A/B testing
• Add tracking headers
• Set custom cookies

Performance characteristics:

• Runs on edge nodes closest to users
• Sub-10ms execution time
• Doesn't block server rendering
• Automatic global deployment

AI-Friendly Design:

Middleware in Frontend Accelerator follows clear patterns:

• Single middleware.ts file at project root
• Explicit matcher configuration for protected routes
• Simple conditional logic for redirects
• Type-safe request/response objects

Limitations:

• Cannot access full Node.js APIs (edge runtime only)
• Limited to 1MB execution size
• No access to filesystem

Middleware can be used for authentication, but also for custom business logic that needs to run before request processing.