Request collapsing for ISR cache misses
By Steven Van ·
Vercel's CDN now runs one function invocation per region to regenerate an expired ISR page, no matter how many requests arrive at once.
The Vercel CDN now applies request collapsing to Incremental Static Regeneration (ISR) pages: when a cached page expires and several requests arrive for the same path at once, only one function invocation per region regenerates it, and the rest wait and receive the same cached response once it's ready.
Previously, each of those simultaneous requests could trigger its own regeneration, a "cache stampede" that wastes compute and can overload backends. The CDN determines which routes are cacheable automatically from framework metadata, so no configuration is needed. If a lock can't be acquired within a few seconds, a waiting request proceeds to invoke the function itself rather than waiting indefinitely. The feature is enabled by default for all projects using ISR. According to Vercel's announcement, it currently collapses over 3 million cache-miss requests per day in production.
