Building Scalable React Applications

Building a React app that can grow with your business does not require fancy architecture or complex patterns. It requires discipline around a few simple ideas that make a big difference over time.

Keep Components Small

The single biggest thing you can do for scalability is keep your components focused on one job.

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The 150 Line Rule

If a component exceeds 150 lines of code, it is probably doing too much. Split it into smaller pieces.

Here is what splitting looks like in practice:

// Before: One giant component doing everything
function UserProfile() {
  // 200+ lines of profile, settings, avatar, activity...
}

// After: Focused components
function UserProfile() {
  return (
    <div>
      <UserAvatar />
      <UserInfo />
      <UserActivity />
    </div>
  )
}

Each piece is easier to test, reuse, and understand.

Organize Files by Feature

Forget about having one giant components/ folder. Group related files together instead.

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Feature-Based Structure

When everything related to a feature lives together, you spend less time hunting for files.

src/
  features/
    auth/
      LoginForm.tsx
      useAuth.ts
      auth.utils.ts
    dashboard/
      Dashboard.tsx
      DashboardCard.tsx
      useDashboardData.ts

This structure scales because adding new features does not clutter existing folders.

Start Simple with State

One of the biggest mistakes in React apps is reaching for complex state management too early.

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State Management Starting Point

Start with useState for component state. Only add Context or external libraries when you genuinely need to share state across many components.

Here is the progression:

useState - Local component state
useContext - Share state between a few related components
External library - When you have complex state logic or need time-travel debugging

// Start here
const [user, setUser] = useState(null)

// Move to Context when multiple components need it
const UserContext = createContext(null)

// Only reach for Redux/Zustand when you truly need it

Performance Quick Wins

Most React performance problems come from unnecessary re-renders.

⚠️

Common useEffect Mistake

Forgetting to add dependencies to useEffect causes either infinite loops or stale data. Always check your dependency array.

// Missing dependency - will use stale userId
useEffect(() => {
  fetchUser(userId)
}, []) // userId should be here

// Correct
useEffect(() => {
  fetchUser(userId)
}, [userId])

💎

When to Use React.memo

Use React.memo on components that receive the same props frequently but their parent re-renders often. Do not wrap everything.

// Good candidate - receives stable props from frequently updating parent
const ExpensiveList = React.memo(function ExpensiveList({ items }) {
  return items.map(item => <ListItem key={item.id} {...item} />)
})

Key Takeaways

Building scalable React apps comes down to:

Keep components under 150 lines
Organize by feature, not by type
Start with useState, add complexity only when needed
Watch your useEffect dependencies
Use React.memo strategically, not everywhere

These simple practices compound over time. Your future self will thank you.