runtime-cache

Import getCache from @vercel/functions, then call cache.set with a key, value, TTL, and tags, and cache.get to retrieve values. The cache is scoped per project, per region, and per deployment environment.

Call cache.expireTag('tag') to invalidate Runtime Cache entries, which propagates globally within 300ms. To purge across CDN, Runtime, and Data caches together, use invalidateByTag or dangerouslyDeleteByTag from @vercel/functions.

'use cache' stores data in-memory per instance and is ephemeral, while 'use cache: remote' stores data in the Vercel Runtime Cache shared across functions in a region. The remote directive requires Next.js 16 with cacheComponents enabled.

No, Runtime Cache tags do not apply to ISR pages, and revalidatePath or revalidateTag do not invalidate the Runtime Cache. Use invalidateByTag with a shared tag to purge all cache layers at once.

Items are limited to 2 MB, with up to 64 tags per Runtime Cache item and 128 per CDN item. Tags are case-sensitive, cannot contain commas, and are capped at 256 bytes; storage is ephemeral with LRU eviction when full.

Avoid it for persistent storage, cross-region shared state, user-specific per-request data, or framework-level page caching. Use a database like Neon or Upstash for persistence and Cache-Control headers for CDN-level full response caching.