1---
2title: Cross-Request LRU Caching
3impact: HIGH
4impactDescription: caches across requests
5tags: server, cache, lru, cross-request
6---
7 
8## Cross-Request LRU Caching
9 
10`React.cache()` only works within one request. For data shared across sequential requests (user clicks button A then button B), use an LRU cache.
11 
12**Implementation:**
13 
14```typescript
15import { LRUCache } from 'lru-cache'
16 
17const cache = new LRUCache<string, any>({
18  max: 1000,
19  ttl: 5 * 60 * 1000  // 5 minutes
20})
21 
22export async function getUser(id: string) {
23  const cached = cache.get(id)
24  if (cached) return cached
25 
26  const user = await db.user.findUnique({ where: { id } })
27  cache.set(id, user)
28  return user
29}
30 
31// Request 1: DB query, result cached
32// Request 2: cache hit, no DB query
33```
34 
35Use when sequential user actions hit multiple endpoints needing the same data within seconds.
36 
37**With Vercel's [Fluid Compute](https://vercel.com/docs/fluid-compute):** LRU caching is especially effective because multiple concurrent requests can share the same function instance and cache. This means the cache persists across requests without needing external storage like Redis.
38 
39**In traditional serverless:** Each invocation runs in isolation, so consider Redis for cross-process caching.
40 
41Reference: [https://github.com/isaacs/node-lru-cache](https://github.com/isaacs/node-lru-cache)
42