# Preventing the stampede: Request collapsing in the Vercel CDN

By Steven Van · 2025-09-25

Vercel's CDN now limits duplicate ISR and Image Optimization requests to one function invocation per region during traffic spikes.

The [Vercel](<https://creatorstoolbox.com/tools/vercel>) CDN now uses [request collapsing](<https://vercel.com/docs/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.

![Vercel](<https://www.google.com/s2/favicons?domain=vercel.com&sz=128>)

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[Original source](<https://vercel.com/docs/request-collapsing>)

[Read Preventing the stampede: Request collapsing in the Vercel CDN on Creators Toolbox](<https://creatorstoolbox.com/blog/vercel-preventing-the-stampede-request-collapsing-in-the-vercel-cdn>)

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Canonical source: https://creatorstoolbox.com/blog/vercel-preventing-the-stampede-request-collapsing-in-the-vercel-cdn