Vanta India Frontend Engineer Interview: Rounds, Questions and Preparation

What the job involves

Frontend engineers at global tech companies like Vanta India build and maintain user-facing web applications, often focused on dashboards, data visualisation, and interactive components. They collaborate with designers, backend engineers, and product managers to ship features that are fast, accessible, and reliable. Day to day work includes writing React or similar framework code, reviewing pull requests, debugging UI issues, and optimising performance.

Role and Technical Knowledge

1. 1

   Explain the difference between `let`, `const`, and `var` in JavaScript. When would you use each?

   Cover block scoping, hoisting, and reassignment. Mention that `const` prevents reassignment but not mutation of objects, and that `var` is function-scoped and generally avoided in modern code.

2. 2

   How does the virtual DOM work in React, and why is it useful for building complex UIs like dashboards?

   Explain that React creates a lightweight in-memory representation of the UI, diffs it against the previous version, and updates only the changed parts in the real DOM. This improves performance for dynamic, data-heavy interfaces.

3. 3

   What are the key considerations for making a web application accessible? Give examples.

   Mention semantic HTML, keyboard navigation, ARIA labels, colour contrast, and focus management. Give a concrete example like using `<button>` instead of a clickable `<div>` and adding alt text for images.

4. 4

   How would you optimise the performance of a React application that loads a large table of data?

   Discuss virtualisation (e.g., react-window), pagination or infinite scrolling, memoisation (React.memo, useMemo), code splitting, and avoiding unnecessary re-renders. Mention measuring with React DevTools Profiler.

Practical Scenarios

1. 5

   You need to build a reusable modal component that can be opened from multiple places in the app. How would you design it?

   Cover props for content and visibility, using React portals to render outside the parent DOM hierarchy, handling escape key and click outside to close, and accessibility features like focus trap and ARIA roles.

2. 6

   A user reports that a form submission button sometimes does not work. How would you debug this?

   Outline steps: reproduce the issue, check browser console for errors, inspect network requests, verify event handlers and state updates, test across browsers, and add logging. Mention using React DevTools to inspect component state.

3. 7

   You are asked to integrate a third-party API that returns data in a nested JSON format. How would you fetch and display it?

   Describe using fetch or axios with async/await, handling loading and error states, normalising the data if needed, and rendering with a component that maps over the array. Mention caching or state management if the data is used in multiple places.

4. 8

   How would you ensure a responsive layout works well on both mobile and desktop for a complex dashboard?

   Discuss using CSS Grid and Flexbox, media queries, relative units, and testing with browser dev tools. Mention mobile-first design and potentially hiding or rearranging less critical information on smaller screens.

Behavioural and HR

1. 9

   Tell me about a time you had to learn a new frontend technology quickly for a project. How did you approach it?

   Use the STAR method: describe the situation, the technology, your learning strategy (docs, tutorials, small prototypes), and the outcome. Highlight curiosity and ability to apply knowledge under time pressure.

2. 10

   Describe a situation where you disagreed with a teammate about a technical decision. How did you handle it?

   Focus on respectful communication, listening to their perspective, providing data or examples to support your view, and ultimately aligning with the team's decision. Show that you value collaboration over being right.

3. 11

   Why do you want to work as a frontend engineer at a company like Vanta India?

   Connect your interest in building user-friendly interfaces with the company's focus on security or compliance dashboards. Mention specific aspects like working with modern frameworks, solving complex UI problems, and contributing to products that help businesses.

4. 12

   Where do you see yourself in the next two years as a frontend engineer?

   Show ambition to deepen technical skills (e.g., mastering React, performance optimisation, accessibility) and take on more ownership, while remaining a team player. Avoid saying you want to move into management immediately.

Coding and Problem Solving

1. 13

   Write a function that takes an array of objects and returns a new array with only the objects that have a specific property value.

   Use `Array.prototype.filter` with a callback that checks the property. Discuss time complexity (O(n)) and edge cases like empty array or missing property.

2. 14

   Given a string, write a function to check if it is a palindrome, ignoring case and non-alphanumeric characters.

   Normalise the string by converting to lowercase and removing non-alphanumeric characters, then compare with its reverse. Mention using two pointers for efficiency if needed.

3. 15

   Implement a simple debounce function in JavaScript. Explain its use case in a frontend context.

   Write a function that delays invoking the provided function until after a specified wait time has elapsed since the last call. Use cases include search input, window resize, or scroll events to limit API calls or expensive computations.

4. 16

   How would you find the first non-repeating character in a string? Write the code.

   Use a hash map to count occurrences, then iterate through the string to find the first character with count 1. Discuss time and space complexity (both O(n)).