Preventing the stampede: Request collapsing in the Vercel CDN

The Vercel CDN now supports request collapsing for ISR routes. For a given path, only one function invocation per region runs at once, no matter how many concurrent requests arrive.

When you deploy a Next.js app with Incremental Static Regeneration (ISR), pages get regenerated on-demand after their cache expires. ISR lets you get the performance benefits of static generation while keeping your content fresh.But there's a problem. When many users request the same ISR route at once and the cache is expired, each request can trigger its own function invocation. This is called a "cache stampede." It wastes compute, overloads your backend, and can cause downtime.The Vercel CDN now prevents this with request collapsing. When multiple requests hit the same uncached path, only one request per region invokes a function. The rest wait and get the cached response.Vercel automatically infers cacheability for each request through framework-defined infrastructure, configuring our globally distributed router. No manual configuration needed.