PayPay || SDE 2 || Interview Experience || Feb 2026
Summary
I interviewed for an SDE 2 Backend Developer role at PayPay in Gurgaon and successfully cleared all five rounds, including technical, system design, and HR, leading to my selection.
Full Experience
Role - Backend developer
Location - Gurgaon
Experience - 3 years 9 months
Round 0 - Online Assessment
4 questions on Code signal platform - all 4 had to be solved correctly. 2 were easy, 1 was medium, 1 was hard
Round 1 - Technical Round 1
- How did you optimize the running time of your projects?
- Which database did you use in your project and why? Why not NoSQL Database? Difference between SQL and NoSQL.
- How does NoSQL support horizontal scalability? Tell about ACID and CAP theorem. Are consistency and availability both possible simultaneously?
- Tell about isolation levels and indices in SQL database. Advantages and disadvantages of indices.
- What is idempotency in API and how can it be achieved? Difference between Put and Patch.
- Difference between optimistic and pessimistic locking.
- Time complexity of insertion/ accessing an element in a BST.
- DSA question - https://leetcode.com/problems/max-consecutive-ones-iii/description/
Verdict - Positive
Round 2- Technical Round 2
- Find maximum path sum in any tree on a downward path (full working code), follow-up question - what if the path can be in any direction, not necessarily downwards
- How will you avoid double payment by a user while designing the APIs in a payment system?
- Suppose a user is performing an action from multiple devices, for eg. ticket booking, but that action should be reflected only once- how will you handle this?
- What would you do if redis cache memory is exhausted?
Verdict - Positive
Round 3 - Technical Round 3
- Project Discussion, Follow Up Questions
- Discussion of LLD of Ticket Master Website - requirements specification, entities, database schema design, APIs design
- Discussion on HLD of the system
- How to handle concurrent bookings?
- In which tables is it advisable to introduce indexing?
- How to make searching of any meta data faster? How does Elastic Search sync with the database?
Verdict - Positive
Round 4- HR Round - This round consisted of background check and basic HR questions.
Round 5 - Techno-Managerial Round
This round was a mix of technical and managerial questions.
- Discussion on resume and past projects with follow up questions
- Tell a situation when you got a critical negative feedback
- Tell about a situation when you pushed your limits
- Tell a situation when you had disagreement with teammates
- Reason of switch and expectations with the new role
Verdict - Positive
Overall - Selected
Interview Questions (21)
Project Optimization Techniques
Discussed how I optimized the running time of my projects.
Database Selection & Comparison
Discussed database choices in projects, reasons for SQL over NoSQL, and the differences between SQL and NoSQL databases.
NoSQL Scalability & Distributed Systems Concepts
Explanation of how NoSQL supports horizontal scalability. Discussion on ACID properties and the CAP theorem. Whether consistency and availability are simultaneously possible.
SQL Database Isolation Levels & Indexing
Discussion on isolation levels and indices in SQL databases, including their advantages and disadvantages.
API Idempotency & HTTP Methods
What is idempotency in APIs and how can it be achieved? Difference between HTTP PUT and PATCH methods.
Optimistic vs. Pessimistic Locking
Discussed the difference between optimistic and pessimistic locking mechanisms.
BST Time Complexity
Discussed the time complexity for insertion and accessing an element in a Binary Search Tree (BST).
Max Consecutive Ones III
Given a binary array nums and an integer k, return the maximum number of consecutive 1's in the array if you can flip at most k 0's.
Maximum Path Sum in Binary Tree
Find the maximum path sum in any tree on a downward path. Follow-up: what if the path can be in any direction, not necessarily downwards?
Preventing Double Payments in Payment System
Discussed API design strategies to prevent double payments by a user in a payment system.
Handling Concurrent Actions from Multiple Devices
Discussed how to handle a scenario where a user performs an action (e.g., ticket booking) from multiple devices, ensuring it's reflected only once.
Redis Cache Exhaustion Handling
Discussed strategies and actions to take if Redis cache memory is exhausted.
Low-Level Design (LLD) of Ticket Master Website
Detailed discussion on the Low-Level Design (LLD) of a Ticket Master-like website, covering requirements specification, entity modeling, database schema design, and API design.
High-Level Design (HLD) of a System
Discussion on the High-Level Design (HLD) of a system.
Handling Concurrent Bookings
Discussed strategies for handling concurrent bookings in a system.
Database Indexing Strategy
Discussed criteria and scenarios for introducing indexing in database tables.
Optimizing Metadata Search & ElasticSearch Sync
Discussed methods to make searching of metadata faster and how ElasticSearch syncs with a primary database.
Handling Critical Negative Feedback
Behavioral question: Describe a situation where you received critical negative feedback and how you handled it.
Pushing Limits
Behavioral question: Describe a situation where you pushed your limits.
Handling Team Disagreements
Behavioral question: Describe a situation where you had a disagreement with teammates and how you resolved it.
Reason for Switch & Role Expectations
Behavioral question: Discussed reasons for switching jobs and expectations for the new role.