parallel-data-fetching-with-component-composition

---

name: Parallel Data Fetching with Component Composition impact: CRITICAL description: eliminates server-side waterfalls tags: server, rsc, parallel-fetching, composition

Parallel Data Fetching with Component Composition

React Server Components execute sequentially within a tree. Restructure with composition to parallelize data fetching.

Incorrect (Sidebar waits for Page's fetch to complete):

Copyexport default async function Page() {
  const header = await fetchHeader()
  return (
    <div>
      <div>{header}</div>
      <Sidebar />
    </div>
  )
}

async function Sidebar() {
  const items = await fetchSidebarItems()
  return <nav>{items.map(renderItem)}</nav>
}

Correct (both fetch simultaneously):

Copyasync function Header() {
  const data = await fetchHeader()
  return <div>{data}</div>
}

async function Sidebar() {
  const items = await fetchSidebarItems()
  return <nav>{items.map(renderItem)}</nav>
}

export default function Page() {
  return (
    <div>
      <Header />
      <Sidebar />
    </div>
  )
}

Alternative with children prop:

Copyasync function Header() {
  const data = await fetchHeader()
  return <div>{data}</div>
}

async function Sidebar() {
  const items = await fetchSidebarItems()
  return <nav>{items.map(renderItem)}</nav>
}

function Layout({ children }: { children: ReactNode }) {
  return (
    <div>
      <Header />
      {children}
    </div>
  )
}

export default function Page() {
  return (
    <Layout>
      <Sidebar />
    </Layout>
  )
}