React’s flexibility is both a strength and a challenge. Without deliberate architectural decisions, codebases quickly become difficult to navigate, test, and extend. Over multiple production launches, I’ve leaned on a repeatable playbook: folder structure, state boundaries, and composition over configuration.

Folder structure that scales

Avoid organizing by file type (components/, hooks/, utils/). Instead, group by feature or domain. A features/checkout/ folder contains everything needed for checkout: components, hooks, API calls, and tests. This locality reduces cognitive load and makes features portable.

src/
├── features/
│   ├── checkout/
│   │   ├── CheckoutForm.tsx
│   │   ├── useCheckout.ts
│   │   ├── checkoutApi.ts
│   │   └── __tests__/
│   └── catalog/
│       ├── ProductList.tsx
│       ├── useCatalog.ts
│       └── catalogApi.ts
└── shared/
    ├── components/
    └── hooks/

Define clear state boundaries

Not all state belongs in a global store. Distinguish between:

  • Local state: UI toggles, form inputs
  • Shared state: user session, theme
  • Server state: API responses (use React Query or SWR)

Mixing these layers creates coupling. Keep local state local, lift shared state to context or a lightweight store, and delegate server state to a caching library that handles invalidation.

Composition over configuration

React components thrive on composition. Instead of passing dozens of props to configure behavior, compose smaller components:

// ❌ Configuration
<Button variant="primary" size="large" icon="check" />

// ✅ Composition
<Button.Primary>
  <Icon.Check />
  Confirm
</Button.Primary>

Composition surfaces intent and reduces prop drilling. It also makes components easier to test in isolation.

Testing at the right boundaries

Write integration tests that exercise user flows, not implementation details. Use React Testing Library to query by role and text, simulating how users interact with your app. Avoid testing internal state or mocking excessively.

Scalable React applications emerge from consistent patterns, not clever hacks.

By anchoring architecture in features, respecting state boundaries, and favoring composition, your React codebase remains maintainable as it grows from MVP to platform.