CDN cache hit ratio above 80% for static assets

A CDN cache hit ratio below 80% means most static asset requests are reaching your origin server rather than being served from an edge node. Each origin-served request adds 50–400ms of latency depending on user geography, and it multiplies your origin load. ISO 25010:2011 time-behaviour captures the latency cost; the operational consequence is higher infrastructure cost and slower asset delivery specifically for users furthest from your origin region.

Audit your CDN analytics dashboard (Vercel Analytics, Cloudflare, CloudFront) and look for assets with high miss rates. The most common cause is incorrect Cache-Control headers — check that hashed assets carry immutable, max-age=31536000.

// vercel.json — ensure immutable headers reach the CDN edge
{
  "headers": [
    {
      "source": "/_next/static/(.*)",
      "headers": [{ "key": "Cache-Control", "value": "public, max-age=31536000, immutable" }]
    }
  ]
}