Recipes

Edge RuntimePatterns

Deploy serverless functions at the edge with zero cold starts. Route users to the nearest region, stream responses, and keep latency under 50ms worldwide.

Geo-aware routing

Read the x-vercel-ip-country header to serve localized content or redirect users to the nearest replica.

export const runtime = 'edge';

export async function GET(req: Request) {
  const country = req.headers.get('x-vercel-ip-country');
  const locale = country === 'DE' ? 'de' : 'en';
  return Response.json({ locale });
}

Streaming responses

Use the Web Streams API to progressively send chunks. Perfect for AI completions or real-time dashboards.

const encoder = new TextEncoder();
const stream = new ReadableStream({
  start(controller) {
    controller.enqueue(encoder.encode('chunk-1\n'));
    controller.enqueue(encoder.encode('chunk-2\n'));
    controller.close();
  },
});
return new Response(stream);

Know your limits

  • Max 4 MB request body
  • No raw TCP or filesystem access
  • Execution capped at 30 s (hobby) / 60 s (pro)
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