🔥 Web Development Interview Questions with Sample Answers — Part 2

⚡ 11) How do you handle loading states in your app?
👉 Answer: “I use a loading state in React using useState. Before making an API call, I set loading = true. After receiving response, I set it to false. In UI, I conditionally render a loader or spinner while data is loading.”

🔁 12) What is the difference between synchronous and asynchronous code?
👉 Answer: “Synchronous code runs line by line. Asynchronous code allows tasks like API calls to run in background without blocking execution. JavaScript uses async/await or promises to handle async operations.”

🧠 13) How do you prevent unnecessary re-renders in React?
👉 Answer: “I use React.memo for components, useMemo for expensive calculations, and useCallback for functions. Also, I avoid unnecessary state updates.”

📡 14) How do you handle API failures?
👉 Answer: “I use try/catch for async calls. If API fails, I show error messages in UI and sometimes retry logic or fallback UI.”

🔐 15) Where do you store JWT token on frontend?
👉 Answer: “Usually in localStorage or cookies. For better security, HttpOnly cookies are preferred to prevent XSS attacks.”

🗄️ 16) How do you handle large datasets in MongoDB?
👉 Answer: “I use pagination (limit & skip), indexing for faster queries, and aggregation pipelines if needed.”

⚙️ 17) What is middleware in Express and where did you use it?
👉 Answer: “Middleware is a function that runs before request reaches route. I used it for authentication (JWT verification), logging, and parsing JSON.”

🔄 18) How do you ensure data consistency in your app?
👉 Answer: “I validate data on both frontend and backend, use schema validation in Mongoose, and handle edge cases properly.”

🚀 19) How do you improve performance of your backend?
👉 Answer: “I use caching, optimize database queries, add indexing, and reduce unnecessary API calls.”

🌐 20) How do you handle environment variables in production?
👉 Answer: “I use .env files locally and environment settings in deployment platforms like Vercel/Render. Sensitive data like API keys and database URLs are stored securely.”

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