| 1 | --- |
| 2 | title: Parallel Data Fetching with Component Composition |
| 3 | impact: CRITICAL |
| 4 | impactDescription: eliminates server-side waterfalls |
| 5 | tags: server, rsc, parallel-fetching, composition |
| 6 | --- |
| 7 | |
| 8 | ## Parallel Data Fetching with Component Composition |
| 9 | |
| 10 | React Server Components execute sequentially within a tree. Restructure with composition to parallelize data fetching. |
| 11 | |
| 12 | **Incorrect (Sidebar waits for Page's fetch to complete):** |
| 13 | |
| 14 | ```tsx |
| 15 | export default async function Page() { |
| 16 | const header = await fetchHeader() |
| 17 | return ( |
| 18 | <div> |
| 19 | <div>{header}</div> |
| 20 | <Sidebar /> |
| 21 | </div> |
| 22 | ) |
| 23 | } |
| 24 | |
| 25 | async function Sidebar() { |
| 26 | const items = await fetchSidebarItems() |
| 27 | return <nav>{items.map(renderItem)}</nav> |
| 28 | } |
| 29 | ``` |
| 30 | |
| 31 | **Correct (both fetch simultaneously):** |
| 32 | |
| 33 | ```tsx |
| 34 | async function Header() { |
| 35 | const data = await fetchHeader() |
| 36 | return <div>{data}</div> |
| 37 | } |
| 38 | |
| 39 | async function Sidebar() { |
| 40 | const items = await fetchSidebarItems() |
| 41 | return <nav>{items.map(renderItem)}</nav> |
| 42 | } |
| 43 | |
| 44 | export default function Page() { |
| 45 | return ( |
| 46 | <div> |
| 47 | <Header /> |
| 48 | <Sidebar /> |
| 49 | </div> |
| 50 | ) |
| 51 | } |
| 52 | ``` |
| 53 | |
| 54 | **Alternative with children prop:** |
| 55 | |
| 56 | ```tsx |
| 57 | async function Header() { |
| 58 | const data = await fetchHeader() |
| 59 | return <div>{data}</div> |
| 60 | } |
| 61 | |
| 62 | async function Sidebar() { |
| 63 | const items = await fetchSidebarItems() |
| 64 | return <nav>{items.map(renderItem)}</nav> |
| 65 | } |
| 66 | |
| 67 | function Layout({ children }: { children: ReactNode }) { |
| 68 | return ( |
| 69 | <div> |
| 70 | <Header /> |
| 71 | {children} |
| 72 | </div> |
| 73 | ) |
| 74 | } |
| 75 | |
| 76 | export default function Page() { |
| 77 | return ( |
| 78 | <Layout> |
| 79 | <Sidebar /> |
| 80 | </Layout> |
| 81 | ) |
| 82 | } |
| 83 | ``` |
| 84 |