🚀 React Interview Experience (August 2025): Bajaj Finserv

Overview

This case study details a React developer interview conducted in August 2025. The interview process assessed the candidate's proficiency in React, JavaScript, and general frontend development principles. The questions covered a range of topics, including state management, performance optimization, and asynchronous programming.

Interview Rounds

The interview process included questions targeting practical coding skills and theoretical understanding.

Question 1:

The candidate was asked to write a function to find duplicate integers within an array, without using built-in array methods. The provided solution iterates through the array, tracking seen numbers and duplicates using nested loops.

Question 2:

The interviewer inquired about the appropriate use cases for Context API versus Redux. The candidate explained that Context API is suitable for small, infrequent global state, while Redux is better suited for large, complex state requiring advanced features like middleware and debugging tools.

Question 3:

The candidate was asked about their experience with Suspense and Transitions. The candidate described using Suspense for lazy-loading components and displaying fallback UIs during data fetching. They also discussed using useTransition to maintain UI responsiveness during heavy state updates, such as filtering large datasets.

Question 4:

The interviewer probed how concurrent processes or features were managed in React applications. The candidate mentioned useTransition and useDeferredValue for UI concurrency, Promise.all for parallel async tasks, AbortController to avoid race conditions, and React Query/SWR for data fetching optimization.

Question 5:

The candidate was asked to explain the differences between useEffect and useLayoutEffect. The candidate clarified that useEffect runs after the browser paints the UI and is suitable for most side effects, while useLayoutEffect runs synchronously before paint and is necessary for DOM measurements or preventing flicker.

Question 6:

The interviewer asked about methods to prevent re-rendering in React applications. The candidate detailed several strategies: React.memo, useCallback, useMemo, avoiding anonymous functions, splitting components, proper state placement, smaller contexts, virtualization for large lists, and React 18's automatic batching.

Question 7:

The candidate was asked to outline the differences between TypeScript and JavaScript. The candidate highlighted the static typing of TypeScript versus the dynamic typing of JavaScript, as well as the error detection, syntax, compilation, code safety, and ecosystem differences.

Question 8:

The interviewer asked to explain variable scope in JavaScript. The candidate described global, function, block, and module scopes, along with the behavior of var, let, and const.

Question 9:

The candidate was asked to explain the differences between state and props. The candidate clarified that state is data owned and managed by a component, whereas props are data passed to a component from its parent. State is mutable, while props are immutable within the child component.

Question 10:

The interviewer asked the candidate to explain the differences between class components and functional components. The candidate covered syntax, state management, lifecycle methods, this keyword binding, performance considerations, readability, and the use of hooks.

Key Takeaways

This interview experience emphasizes the importance of a strong foundation in React fundamentals, JavaScript concepts, and performance optimization techniques. Candidates should be prepared to discuss state management strategies, asynchronous programming patterns, and methods for preventing unnecessary re-renders. Understanding the differences between TypeScript and JavaScript, as well as variable scoping in JavaScript, is also crucial for success.