livedash-node/.opencode/skills/vercel-react-best-practices/rules/server-parallel-fetching.md

---
title: Parallel Data Fetching with Component Composition
impact: CRITICAL
impactDescription: 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):**

```tsx
export 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):**

```tsx
async 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:**

```tsx
async 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>
  );
}
```