React Architecture Best Practices for Scalable Applications

Why React Architecture Matters

React is deliberately unopinionated. This is a feature, not a bug — but it means architectural decisions that work for a 10-component app break down at 100 components. Teams that defer architecture discussions pay for it in:

• Slow onboarding (no clear pattern for where things go)
• State management spaghetti
• Components that are impossible to test
• Bundle sizes that balloon as features are added carelessly

Folder Structure: Feature-Based Over Type-Based

Bad (type-based):

src/
  components/
    Header.tsx
    UserCard.tsx
    ProductList.tsx
  hooks/
    useAuth.ts
    useProducts.ts
  pages/
    Dashboard.tsx
    Products.tsx

Good (feature-based):

src/
  features/
    auth/
      components/LoginForm.tsx
      hooks/useAuth.ts
      api/authApi.ts
      types.ts
    products/
      components/ProductList.tsx
      hooks/useProducts.ts
      api/productsApi.ts
      types.ts
  shared/
    components/Button.tsx
    hooks/useDebounce.ts
    utils/formatDate.ts
  pages/
    Dashboard.tsx   ← composes features
    Products.tsx

Feature-based structure means everything related to a feature lives together. Deleting a feature is one folder deletion. Adding a developer to a feature means they only need to understand one directory.

Component Design: Single Responsibility

Each component should do one thing. The litmus test: can you describe what this component does in one sentence without using "and"?

Split components by:

• Presentation (dumb) vs container (smart) where appropriate
• Route-level vs shared components
• Domain logic vs UI

Keep components under 200 lines. If a component grows beyond that, it is doing too much.

State Management: Two Types, Two Solutions

Many teams make the mistake of putting server data (API responses) into Redux or Zustand alongside UI state. This leads to complex synchronisation logic that React Query/TanStack Query solves out of the box.

State Type	Solution	Examples
Server state	TanStack Query (React Query)	User profile, product list, orders
Global client state	Zustand or Jotai	Auth status, theme, sidebar open/closed
Local UI state	useState / useReducer	Form values, modal open, hover state

Rule of thumb: if the data lives on a server, use React Query. If it is pure client-side UI state, use useState or Zustand.

Custom Hooks: Separate Logic from UI

Business logic in JSX is untestable and unreadable. Extract it into custom hooks:

// Bad: logic mixed into component
function ProductList() {
  const [products, setProducts] = useState([]);
  const [loading, setLoading] = useState(true);
  useEffect(() => {
    fetch('/api/products')
      .then(r => r.json())
      .then(data => { setProducts(data); setLoading(false); });
  }, []);
  return loading ? <Spinner /> : products.map(p => <ProductCard key={p.id} {...p} />);
}

// Good: logic in hook, component is pure UI
function useProducts() {
  return useQuery({ queryKey: ['products'], queryFn: fetchProducts });
}
function ProductList() {
  const { data: products, isLoading } = useProducts();
  if (isLoading) return <Spinner />;
  return products.map(p => <ProductCard key={p.id} {...p} />);
}

Code Splitting and Lazy Loading

Every route should be code-split. Do not ship the entire application in one bundle:

const Dashboard = React.lazy(() => import('./pages/Dashboard'));
const Products = React.lazy(() => import('./pages/Products'));

function App() {
  return (
    <Suspense fallback={<PageLoader />}>
      <Routes>
        <Route path="/dashboard" element={<Dashboard />} />
        <Route path="/products" element={<Products />} />
      </Routes>
    </Suspense>
  );
}

Also lazy-load heavy third-party components (rich text editors, chart libraries, map components) that are not needed on initial render.

TypeScript: Non-Negotiable at Scale

Use TypeScript from day one. Specific rules:

• No any — use unknown if the type is genuinely unknown, then narrow it
• Define prop interfaces explicitly for every component
• Type API responses with generated types (OpenAPI codegen) or manual interfaces
• Enable strict mode in tsconfig

Build your React application on a solid foundation. Talk to our web development team → or contact us to review your current architecture.

The Architecture Mistakes That Slow Teams Down

The most common React architecture problems we see in codebases we inherit:

Global state used as a first resort: every piece of data placed in Redux or Zustand regardless of whether it actually needs to be global. The rule of thumb: if only one component or one component tree uses a piece of state, it belongs in that component's local state (useState) or passed as props. Global state should be genuinely global — user authentication state, application theme, data needed by deeply separated component trees.

Over-abstraction of components: wrapping every 5 lines of JSX in a new component because "components should be small." The result is files with 20 component definitions, complex prop chains to pass data between them, and a codebase where understanding any feature requires opening 10 files. Components should be extracted when there is a meaningful reason — reuse across different parts of the app, substantial independent testability, or size genuinely making the file hard to navigate.

Missing error boundaries: React applications that have not implemented error boundaries will show a blank white screen to users when a component throws an unexpected error. Implement error boundaries at the route level (each route renders within an error boundary) so that an error in one part of the application does not destroy the entire application.

At Ortem Technologies, we deliver React applications with clear architectural patterns, TypeScript throughout, and component structures that new engineers can understand and extend without archaeology. Talk to our React team | Get a React architecture consultation

The Testing Architecture That Makes Large React Codebases Maintainable

Testing strategy for React applications at scale: unit tests for pure logic functions (utility functions, custom hooks without side effects, state reducer logic) using Jest and React Testing Library, integration tests for complete component trees with mocked API calls, and a small E2E test suite for critical user flows using Playwright or Cypress.

The testing anti-patterns that create maintenance burden: testing implementation details (testing that a component calls a specific function internally rather than testing the visible behavior), using mount instead of render for components that don't need the full DOM tree, and over-testing UI (testing that a button has a specific class name rather than testing that clicking the button produces the expected behavior).

The React Testing Library philosophy — query the DOM as users would interact with it (by text, by role, by label), not by CSS selectors or component internals — produces tests that remain valid as the implementation changes, reducing maintenance burden as the codebase evolves.

Talk to our React engineering team | Get a React architecture review for your codebase