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SKILL.md
npx skills add openai/plugins --skill runtime-cache
Vercel Runtime Cache API guidance — ephemeral per-region key-value cache with tag-based invalidation. Shared across Functions, Routing Middleware, and Builds. Use when implementing caching strategies beyond framework-level caching.
npx skills add openai/plugins --skill runtime-cache
You are an expert in the Vercel Runtime Cache — an ephemeral caching layer for serverless compute.
The Runtime Cache is a per-region key-value store accessible from Vercel Functions, Routing Middleware, and Builds. It supports tag-based invalidation for granular cache control.
preview vs production)expireTag@vercel/functionsAll APIs from @vercel/functions:
These purge across all three cache layers (CDN + Runtime Cache + Data Cache):
Important distinction:
cache.expireTag() — operates on Runtime Cache onlyinvalidateByTag() / dangerouslyDeleteByTag() — purges CDN + Runtime + Data cachesuse cache: remote)'use cache' (no : remote) — in-memory only, ephemeral per instance'use cache: remote' — stores in Vercel Runtime Cache| Function | Context | Behavior |
|---|---|---|
updateTag(tag) | Server Actions only | Immediate expiration, read-your-own-writes |
revalidateTag(tag, 'max') | Server Actions + Route Handlers | Stale-while-revalidate (recommended) |
revalidateTag(tag, { expire: 0 }) | Route Handlers (webhooks) | Immediate expiration from external triggers |
Important: Single-argument revalidateTag(tag) is deprecated in Next.js 16. Always pass a cacheLife profile as the second argument.
cache.expireTag does NOT invalidate ISR cacherevalidatePath / revalidateTag does NOT invalidate Runtime CacheinvalidateByTag (hits all cache layers)Note: --tag and --srcimg cannot be used together.
Add tags to CDN cached responses for later invalidation:
| Property | Limit |
|---|---|
| Item size | 2 MB |
| Tags per Runtime Cache item | 64 |
| Tags per CDN item | 128 |
| Max tag length | 256 bytes |
| Tags per bulk REST API call | 16 |
Tags are case-sensitive and cannot contain commas.
Monitor hit rates, invalidation patterns, and storage usage in the Vercel Dashboard under Observability → Runtime Cache. The CDN dashboard (March 5, 2026) provides a unified view of global traffic distribution, cache performance metrics, a redesigned purging interface, and project-level routing — update response headers or rewrite to external APIs without triggering a new deployment. Project-level routes are available on all plans and take effect instantly.
'use cache')Cache-Control / Vercel-CDN-Cache-Control headersconst cache = getCache({
namespace: 'api', // prefix for keys
namespaceSeparator: ':', // separator (default)
keyHashFunction: (key) => sha256(key), // custom key hashing
});import { getCache } from '@vercel/functions';
export default {
async fetch(request: Request) {
const cache = getCache();
const cached = await cache.get('blog-posts');
if (cached) {
return Response.json(cached);
}
const posts = await fetch('https://api.example.com/posts').then(r => r.json());
await cache.set('blog-posts', posts, {
ttl: 3600,
tags: ['blog'],
});
return Response.json(posts);
},
};'use server';
import { getCache } from '@vercel/functions';
export async function invalidateBlog() {
await getCache().expireTag('blog');
}import { invalidateByTag, dangerouslyDeleteByTag } from '@vercel/functions';
// Stale-while-revalidate: serves stale, revalidates in background
await invalidateByTag('blog-posts');
// Hard delete: next request blocks while fetching from origin (cache stampede risk)
await dangerouslyDeleteByTag('blog-posts', {
revalidationDeadlineSeconds: 3600,
});// next.config.ts
const nextConfig: NextConfig = { cacheComponents: true };import { cacheLife, cacheTag } from 'next/cache';
async function getData() {
'use cache: remote' // stores in Vercel Runtime Cache
cacheTag('example-tag')
cacheLife({ expire: 3600 })
return fetch('https://api.example.com/data').then(r => r.json());
}# Purge all cached data
vercel cache purge # CDN + Data cache
vercel cache purge --type cdn # CDN only
vercel cache purge --type data # Data cache only
vercel cache purge --yes # skip confirmation
# Invalidate by tag (stale-while-revalidate)
vercel cache invalidate --tag blog-posts,user-profiles
# Hard delete by tag (blocks until revalidated)
vercel cache dangerously-delete --tag blog-posts
vercel cache dangerously-delete --tag blog-posts --revalidation-deadline-seconds 3600
# Image invalidation
vercel cache invalidate --srcimg /images/hero.jpgimport { addCacheTag } from '@vercel/functions';
// Via helper
addCacheTag('product-123');
// Via response header
return Response.json(product, {
headers: {
'Vercel-CDN-Cache-Control': 'public, max-age=86400',
'Vercel-Cache-Tag': 'product-123,products',
},
});