Upstox SDE-2 (Frontend) Interview Experience — July 2025

Overview

The interview process for the SDE-2 (Frontend) role at Upstox consisted of four stages designed to assess the candidate's technical abilities and cultural fit. The stages included an online assessment, two technical interview rounds, a discussion with the hiring manager, and a final HR discussion. This structured approach ensured a comprehensive evaluation of the candidate's skills in data structures, algorithms, JavaScript fundamentals, React, and system design, all within the context of a financial technology company.

Interview Rounds

Round 1: HackerRank Online Assessment (July 2)

The online assessment consisted of two questions designed to evaluate both DSA and React problem-solving abilities.

• Q1: DSA — Longest Ones (Max Consecutive Ones): A standard array problem involving finding the maximum consecutive ones in a binary array, potentially with constraints such as a limited number of allowed zero flips.
• Q2: React — Stock Buy and Sell Component: This question involved building a simplified trading application. The task required the candidate to implement buy/sell buttons, track transactions, and display the final profit in a separate component. The challenge tested React fundamentals and state management skills.

Round 2: Problem Solving + JavaScript Fundamentals

This technical round focused on DSA, debugging, and core JavaScript concepts. It was conducted live with the interviewer.

• Q1: Search in Rotated Sorted Array: A LeetCode-medium binary search problem. The interviewer inquired about the optimal approach and edge case handling.
• Q2: Output-Based JavaScript Questions: Questions covered the behavior of this in arrow versus normal functions and the implications of closures and their scope.
• Q3: Currying in JavaScript: The candidate was asked to implement a custom currying function, such as sum(1)(2)(3), to return the total. This assessed the understanding of higher-order functions and lexical scoping.

Round 3: Frontend Design & React Deep Dive

This round evaluated design thinking and React optimization skills.

• Q1: Polyfill for Deep Copy: The task involved implementing a custom deep copy function that correctly handles arrays and nested objects. Follow-up discussions explored corner cases like circular references and immutability concerns.
• Q2: React Optimization Concepts: Topics included when to use React.memo, how useMemo and useCallback optimize renders, and identifying unnecessary re-renders in a large component tree.
• Q3: Design Problem — Upstox Admin Panel: The candidate was asked to design and implement a simplified version of the Upstox admin panel, including a sidebar filter for adding or modifying stocks and a horizontal stock list display. JSON-based mock data design was required before implementation. The interviewer emphasized functional clarity, data structure design, and state management over visual styling.

Round 4: Hiring Manager Discussion

This round was a conversation-based assessment of the candidate's past projects, React architecture decisions, and performance optimization experience in real-world applications.

Key discussion points included:

• Methods for preventing unnecessary re-renders in stock-related components.
• Usage of React hooks (useMemo, useCallback) for expensive calculations.
• Experience with code splitting, lazy loading, and bundle optimization.

Round 5: HR Discussion

This final round covered expected notice period and joining timeline, work culture, compensation, and general behavioral questions.

Key Takeaways

The Upstox SDE-2 (Frontend) interview process provides a balanced assessment of algorithmic thinking, JavaScript proficiency, and React system design skills. The questions closely resemble real-world frontend challenges encountered in a fintech product environment. Candidates preparing for such a role should revisit core JavaScript concepts, practice React component design and optimization, and be prepared to reason about data flow and component state rather than focusing solely on UI implementation.