1---
2title: Prevent Waterfall Chains in API Routes
3impact: CRITICAL
4impactDescription: 2-10× improvement
5tags: api-routes, server-actions, waterfalls, parallelization
6---
7 
8## Prevent Waterfall Chains in API Routes
9 
10In API routes and Server Actions, start independent operations immediately, even if you don't await them yet.
11 
12**Incorrect (config waits for auth, data waits for both):**
13 
14```typescript
15export async function GET(request: Request) {
16  const session = await auth()
17  const config = await fetchConfig()
18  const data = await fetchData(session.user.id)
19  return Response.json({ data, config })
20}
21```
22 
23**Correct (auth and config start immediately):**
24 
25```typescript
26export async function GET(request: Request) {
27  const sessionPromise = auth()
28  const configPromise = fetchConfig()
29  const session = await sessionPromise
30  const [config, data] = await Promise.all([
31    configPromise,
32    fetchData(session.user.id)
33  ])
34  return Response.json({ data, config })
35}
36```
37 
38For operations with more complex dependency chains, use `better-all` to automatically maximize parallelism (see Dependency-Based Parallelization).
39