Frontend interview Experience at PayPal Bangalore | SDE2 | DSA Heavy

Backend system design even for a frontend role.

Prompt: Design a Payment Gateway System

1. Overall architecture and services breakdown
2. Payment flow between services
3. Transaction processing and idempotency
4. Ledger system for consistency and traceability
5. Reliability and security trade-offs

💡 Payment gateway design is asked in almost every PayPal frontend interview. Prepare it cold.

Proctored. 3 questions covering DSA, JS and React.

1. DSA: String manipulation, LeetCode medium level
2. JavaScript: Implement a class with several methods per spec, OOP-focused
3. React UI : Build a cart management system, with dynamic cart updates, total quantity state, real-time UI sync, and a sample layout given

💡 PayPal screens with React + DSA + OOP in a single round. Skip one area, and you fail here.

Pure DSA. Hidden test cases must pass.

1. Triangle minimum path sum (Dynamic Programming)
2. Min Stack with O(1) push, pop, top and getMin
3. Topological Sort using DFS, approach discussion only

💡 Edge cases are tested with hidden cases. Sample passing is not enough.

DSA + React internals + live coding.

1. Binary search problem, easy level
2. React internals: Virtual DOM, Reconciliation, Diffing algorithm
3. Write pseudocode for the React Diffing Algorithm
4. Build a Currency Converter app: Dropdown selection, dynamic conversion, real time updates, state management

💡 Knowing React is not enough. They want how it works under the hood.