runtime-cache

Vercel Runtime Cache API

You are an expert in the Vercel Runtime Cache — an ephemeral caching layer for serverless compute.

What It Is

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.

• Regional: Each Vercel region has its own isolated cache
• Isolated: Scoped per project AND per deployment environment (preview vs production)
• Persistent across deployments: Cached data survives new deploys; invalidation via TTL or expireTag
• Ephemeral: Fixed storage limit per project; LRU eviction when full
• Framework-agnostic: Works with any framework via @vercel/functions

Key APIs

All APIs from @vercel/functions:

Basic Cache Operations

import { getCache } from '@vercel/functions';

const cache = getCache();

// Store data with TTL and tags
await cache.set('user:123', userData, {
  ttl: 3600,                      // seconds
  tags: ['users', 'user:123'],    // for bulk invalidation
  name: 'user-profile',           // human-readable label for observability
});

// Retrieve cached data (returns value or undefined)
const data = await cache.get('user:123');

// Delete a specific key
await cache.delete('user:123');

// Expire all entries with a tag (propagates globally within 300ms)
await cache.expireTag('users');
await cache.expireTag(['users', 'user:123']); // multiple tags

Cache Options

const cache = getCache({
  namespace: 'api',                    // prefix for keys
  namespaceSeparator: ':',             // separator (default)
  keyHashFunction: (key) => sha256(key), // custom key hashing
});

Full Example (Framework-Agnostic)

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);
  },
};