Preventing the stampede: Request collapsing in the Vercel CDN
By Steven Van ·
Vercel's CDN now limits duplicate ISR and Image Optimization requests to one function invocation per region during traffic spikes.
The Vercel CDN now uses request collapsing to stop cache stampedes on uncached routes. When a page built with Incremental Static Regeneration expires and many requests hit it at once, only one request per region triggers a function invocation. The rest wait and receive the same cached response once it's ready, rather than each kicking off its own regeneration.
Vercel also applies request collapsing to stale-while-revalidate responses, so concurrent background revalidations collapse into a single invocation. It works automatically, with no manual configuration, and currently covers Incremental Static Regeneration and Image Optimization.