React Deployment & Best Practices — Interview Questions & Answers

Ques1. What does “building for production” mean in React?

Ans: Building for production means optimizing your React app for performance and efficiency before deploying it to users.

It includes:

• Minifying JavaScript and CSS files.
• Optimizing images.
• Removing development warnings.
• Creating a static build using npm run build.

Ques2. How do you create a production build in React?

Ans: Run the command:

npm run build

This generates a build/ folder containing optimized files (HTML, JS, CSS, and assets) ready for deployment.

Ques3. Why is minification important in production builds?

Ans: Minification removes unnecessary spaces, comments, and unused code, reducing file size and improving page load times.

Ques4. What is code splitting in React?

Ans: Code splitting breaks your app into smaller bundles so users only download what they need.

It improves performance by reducing initial load time.

Example using React’s lazy and Suspense:

const About = React.lazy(() => import('./About'));

Ques5. How does React handle environment variables?

Ans: React allows you to define environment variables in .env files:

REACT_APP_API_URL=https://api.example.com

These are accessed using process.env.REACT_APP_API_URL.

Ques6. Why use environment variables in React?

Ans: They help manage different configurations for development, staging, and production without changing code.

Q7. What are common environment variable files in React?

• .env.development
• .env.production
• .env.test

React automatically picks the correct file based on the build environment.

Ques8. What are popular platforms for deploying React apps?

• Netlify – easy drag-and-drop or Git integration.
• Vercel – optimized for React & Next.js.
• GitHub Pages – good for static sites.
• Firebase Hosting – secure and scalable.
• AWS Amplify – enterprise-level hosting.

Ques9. How do you deploy a React app to Netlify?

1. Push your project to GitHub.
2. Connect the repo to Netlify.
3. Set the build command: npm run build
4. Set the publish directory: build/
5. Deploy automatically.

Ques10. How do you deploy a React app to Vercel?

1. Import your GitHub repository to Vercel.
2. It auto-detects React.
3. Build and deploy automatically with every commit.

Ques11. What are the advantages of using GitHub Pages for deployment?

• Free hosting for static websites.
• Direct GitHub integration.
• Simple to use for personal projects and portfolios.

Ques12. How do you set up GitHub Actions for CI/CD in React?

• Add a .github/workflows/deploy.yml file.
• Define steps to install, build, and deploy automatically after each push.

Example:

name: Build and Deploy
on: [push]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - run: npm install
      - run: npm run build

Ques13. What is CI/CD in React deployment?

Ans: CI/CD (Continuous Integration/Continuous Deployment) automates testing, building, and deploying React apps every time code changes — ensuring consistency and faster releases.

Ques14. What is bundle optimization in React?

Ans: Bundle optimization means reducing the size of JavaScript bundles using:

• Tree Shaking – removes unused imports.
• Dynamic Imports – loads code on demand.
• Minification and Compression.

Ques15. What is Tree Shaking in React?

Ans: Tree Shaking automatically removes unused code from the final bundle using tools like Webpack or Rollup.

Ques16. What is lazy loading in React?

Ans: Lazy loading delays loading of components until they are needed, improving performance and reducing initial bundle size.

Example:

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

Ques17. What is React’s Suspense used for in lazy loading?

Ans: Suspense provides a fallback (like a loader) while waiting for a lazy-loaded component.

Example:

<Suspense fallback={<div>Loading...</div>}>
  <Dashboard />
</Suspense>

Ques18. How can you optimize images in React for performance?

• Use modern formats like WebP.
• Compress images before upload.
• Use lazy loading for off-screen images.
• Use CDNs for faster delivery.

Ques19. How can you manage large state efficiently in React?

• Use Context API or Redux Toolkit for global state.
• Split large components.
• Memoize expensive calculations with useMemo or useCallback.

Ques20. What are coding best practices for scalable React apps?

• Follow proper folder structure (components, hooks, pages, etc.)
• Use reusable components.
• Keep logic separate using custom hooks.
• Avoid prop drilling.
• Write readable, commented code.

Ques21. Why is folder structure important in React?

Ans: A consistent project structure improves maintainability, scalability, and team collaboration. Example:

src/
 ┣ components/
 ┣ hooks/
 ┣ pages/
 ┣ utils/
 ┗ App.js

Ques22. How do you handle runtime errors gracefully in production?

Ans: Use React Error Boundaries to catch and handle component-level errors without crashing the app:

componentDidCatch(error, info) {
  console.log(error, info);
}

Ques23. What tools can be used for monitoring deployed React apps?

• Sentry – for error logging.
• LogRocket – for session replay.
• Google Analytics – for performance metrics.
• Lighthouse – for performance auditing.

Ques24. What is the difference between Development and Production mode in React?

Ques25. How can you reduce re-renders and improve performance in React production?

Ans:

• Use React.memo() for pure components.
• Use useCallback() for stable function references.
• Avoid unnecessary state updates.
• Split components efficiently.