Edge Network & CDN

7. Edge Network & CDN

7.1 How the edge network works

Vercel's CDN has PoPs (Points of Presence) around the world. When a user makes a request:

1. Request hits the nearest PoP
2. PoP checks its cache
   • Cache hit: Returns response in milliseconds (sub-10ms)
   • Cache miss: Routes to the nearest Vercel Function region, executes, returns and caches response

7.2 Cache hierarchy

User → Edge PoP Cache → Regional Function Cache → Origin Function
         (ms)              (10-50ms)                  (100ms+)

7.3 Cache-Control headers

Vercel respects standard Cache-Control headers and maps them to CDN cache behaviour:

// Cache for 1 hour, allow stale for 1 day while revalidating
export async function GET() {
  return Response.json(data, {
    headers: {
      'Cache-Control': 's-maxage=3600, stale-while-revalidate=86400'
    }
  });
}

7.4 Skew protection

When a new deployment rolls out, some users may still have old JavaScript from the previous deployment while the server is already running new code — causing version skew errors.

Vercel's Skew Protection (Enterprise + Pro) routes requests to the deployment version that served the original HTML to that user, ensuring consistency. This is a strong enterprise selling point.