Cursor rule

1---
2alwaysApply: false
3---
4 
5## Parallel Nested Data Fetching
6 
7When fetching nested data in parallel, chain dependent fetches within each item's promise so a slow item doesn't block the rest.
8 
9**Incorrect (a single slow item blocks all nested fetches):**
10 
11```tsx
12const chats = await Promise.all(
13  chatIds.map(id => getChat(id))
14)
15 
16const chatAuthors = await Promise.all(
17  chats.map(chat => getUser(chat.author))
18)
19```
20 
21If one `getChat(id)` out of 100 is extremely slow, the authors of the other 99 chats can't start loading even though their data is ready.
22 
23**Correct (each item chains its own nested fetch):**
24 
25```tsx
26const chatAuthors = await Promise.all(
27  chatIds.map(id => getChat(id).then(chat => getUser(chat.author)))
28)
29```
30 
31Each item independently chains `getChat` → `getUser`, so a slow chat doesn't block author fetches for the others.
32