52 questions · from 15 interviews · 1 asked more than once
Paytm interview questions
Every question candidates reported from their Paytm interviews, most frequently asked first. Each links to the write-up it came from, so you can see the round and how it went.
Paytm coding and DSA questions
- 01
Rotten Oranges
Rotten Orange problem – determine the minimum time required to rot all oranges in a grid.
Asked 2 times · From Paytm | Senior Software Engineer
- 02
Linked List Cycle Detection with Variable Fast/Slow Steps
Given a singly linked list, detect if a cycle exists. Additionally, discuss how the algorithm behavior changes if the slow and fast pointers move by steps of (1,3) or (2,4) instead of the classic (1,2).
- 03
Minimum Coins to Make Amount
Given a target amount and an unlimited supply of coins of given denominations, find the minimum number of coins needed to make the amount. Greedy approach does not work; need to explore all possibilities.
- 04
Find First and Last Position of Element in Sorted Array
Given a sorted array and a target value, return the first and last index of the target in the array. Use binary search to achieve O(log n) time.
- 05
Subset Sum
Given an array of positive integers and a target, determine whether there exists a subset whose sum equals the target. If found, print any valid subset; otherwise print "No subset found". Example arr = [3, 34, 4, 12, 5, 2] target = 9
- 06
Longest Palindromic Subsequence
Longest palindromic subsequence (direct from LeetCode).
- 07
KMP Algorithm Variation
A slight variation of the KMP algorithm problem.
- 08
Koko Eating Bananas
Koko eating banana problem – find the minimum eating speed for Koko to finish all bananas within a given number of hours.
- 09
Circular Particle Collision with Mass
You are given an integer array arr representing particles moving on a circular track. - Each element represents a particle. - The absolute value represents the mass of the particle. - The sign represents the direction: - Positive (+) → clockwise - Negative…
Hard · From Paytm SSE Noida Interview experience
- 10
LRU Cache Design
I was asked to design a data structure that follows the constraints of a Least Recently Used (LRU) cache. I needed to implement the get and put operations, both expected to run in O(1) average time complexity. Key focus areas included combining HashMap +…
Medium · From Paytm Technical Lead Interview Experience Feb 2026 (Rejected)
- 11
Course Schedule - Cycle Detection
Given the total number of courses I had to take and a list of prerequisite pairs, I was asked to determine if I could finish all courses. In other words, detect if it's possible to complete all courses given their prerequisites (similar to LeetCode 207).
Medium · From Paytm Technical Lead Interview Experience Feb 2026 (Rejected)
- 12
Longest Substring Without Repeating Characters
Given a string s , find the length of the longest substring without repeating characters.
- 13
Combination Sum
Given a set of candidate numbers candidates (without duplicates) and a target number target , find all unique combinations in candidates where the candidate numbers sum to target . The same repeated number may be chosen from candidates an unlimited number of…
- 14
Longest Common Substring
I was given the classic Longest Common Substring problem in the online assessment, which I solved completely.
- 15
Trapping Rain Water
The interviewer started with the Trap Rain Water problem. I was able to come up with a working solution after some discussion. The interviewer asked me to code it, but since the implementation was taking longer than expected, we skipped the full code.
Hard · From Paytm Senior Technical Lead | Reject
- 16
Left View of a Binary Tree
The next problem was Left View of a Binary Tree. I was able to explain the logic quickly and successfully implemented the code during the interview.
Medium · From Paytm Senior Technical Lead | Reject
- 17
Low-Level Design: MS Paint-like Canvas Fill Backend
Users can draw closed shapes. If they click inside, the entire shape should be filled. Clicking outside fills only that pixel.
- 18
First Negative Integer in Every Window
Given an array and a window size k, find the first negative integer in every window.
Medium · From Paytm Interview Experience (SDE-1)
- 19
Implement LRU Cache
Implement an LRU (Least Recently Used) Cache with efficient get and put operations using suitable data structures.
Medium · From Paytm Interview Experience (SDE-1)
- 20
Unique Paths
A robot is located at the top-left corner of an m x n grid (marked 'Start' in the diagram). The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked 'Finish' in the diagram).…
Medium · From PAYTM | SDE-2
- 21
Search in Rotated Sorted Array
Given a sorted array that has been rotated at some pivot point, find a target value in it. The array has no duplicate elements. Your algorithm's runtime complexity must be in the order of O(log n).
Medium · From PAYTM | SDE-2
- 22
Find Kth Node From End of Linked List
Given the head of a singly linked list, return the k th node from the end of the list. You are guaranteed that k is less than or equal to the number of nodes in the list.
Easy · From PAYTM | SDE-2
- 23
Kadane's Algorithm Variation
I was asked to solve a problem that involved a variation of Kadane's algorithm, which required applying its core logic to a slightly modified problem statement.
- 24
Break Cycle in Linked List
The problem involved detecting a cycle in a given linked list and then modifying the list to break that cycle.
Medium · From Paytm | SSE | October 2023 Offer
- 25
Maximum Sum Path in Binary Tree
I was asked to find the maximum sum path between any two nodes in a binary tree, where the path could start and end at any node.
Hard · From Paytm | SSE | October 2023 Offer
Paytm system design questions
- 01
Design a real‑time market data streaming system
Design the system that receives the exchange tick stream (NSE/BSE: peak ~1M ticks/second across ~5,000 instruments) and delivers live prices to 5M concurrently connected app users, each watching a watchlist of ~20 instruments. Freshness target: user sees a…
From PayTM Interview HLD Round || Interview Experience || Senior Software Engineer
- 02
Design a stock trading platform with order flow
User buy/sell stocks - place order - app routes to exchange - app shows the positions, holdings. The platform is similar to Groww/Zerodha.
From PayTM Interview HLD Round || Interview Experience || Senior Software Engineer
- 03
Design a Twitter-like System
Core Requirements: Follow / Unfollow users Post a tweet Show user feed Discussion Points: High-level architecture Scalability considerations Feed generation approach (fan-out strategies) Database schema design Extension: Search Tweets by Content Started with…
Hard · From Paytm | SSE (Backend) Interview Experience | Rejected
- 04
Design a Job Scheduler System
Problem Statement: System runs every day at a fixed time window Executes scheduled jobs during this window Key Requirements: Scalability Reliability Exactly-once notification delivery
Hard · From Paytm | SSE (Backend) Interview Experience | Rejected
- 05
Design User Management System (LLD)
Design a Low-Level Design for a user management system. This round required setting up a local editor and using specific MySQL/GORM packages. There was also a discussion about past projects.
- 06
Design Shiprocket-like Order Management System
I was asked to design a system similar to Shiprocket, specifically focusing on order management and payment processing.
- 07
Design System for Video View and Like Counts
Design the system for view count and like count of videos.
Hard · From Paytm Senior Technical Lead | Reject
- 08
How Video Streaming System Works
Explain how a video streaming system works.
- 09
Adaptive Video Quality Switching
Explain how video streaming switches to low video quality.
- 10
System Recovery and Backlog Processing
Your app handles 100 RPS and each task takes 100ms. A 5-minute outage means 30K pending tasks. Once restored, how do you process backlog + new incoming traffic in 5 minutes?
- 11
Kafka Consumer Retry and Dead Letter Queue
If a Kafka consumer fails to process a message, how do you retry it 5 times and eventually discard it?
- 12
PostgreSQL Query Optimization
How does PostgreSQL optimize query execution and data retrieval?
- 13
Kubernetes Service Discovery
Pod IPs change frequently. How do services reliably discover and communicate with each other?
- 14
Designing a Loosely-Coupled Pub/Sub System
How do you implement a loosely-coupled publisher-subscriber architecture?
- 15
Design a UPI-like System
Design a UPI-like system supporting: Multiple types of wallets (e.g., Paytm Wallet, Fastag, etc.) A main bank account linked to the user Required to define proper data models and implement core functionalities like add money, transfer, balance check, and…
- 16
Concurrency Control & Transaction Isolation
Discussed database locking mechanisms (pessimistic vs optimistic) and explained transaction isolation levels: Read Uncommitted, Read Committed, Repeatable Read, and Serializable with examples.
- 17
Distributed Caching with Redis
In-depth discussion on Redis – data structures, TTL, eviction policies, and use-cases. Explained caching strategies: write-through, write-behind, and cache-aside.
- 18
Handling Thread Downtime & System Resilience
Was asked how I would manage thread failures or downtime under high-load or continuous request scenarios. Discussed approaches like thread pools, retries, circuit breakers, and fallback mechanisms to ensure system resilience.
- 19
Print Odd and Even Numbers Using Two Threads
Implement a program that uses two separate threads to print numbers in sequence. One thread should print odd numbers and the other should print even numbers, ensuring the final output is a sorted sequence like 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
From PAYTM | SDE-2
- 20
Design Elevator System
I was tasked with designing a complete elevator system, considering aspects such as multiple elevators, handling floor requests, scheduling algorithms, and ensuring safety and efficiency.
- 21
System Design Scenarios: Caching, Idempotency, Consistency, Scaling
I encountered scenario-based questions that required discussing solutions and trade-offs related to implementing caching strategies, ensuring idempotency, maintaining data consistency in distributed systems, and designing for scalability.
Paytm behavioural and HR questions
- 01
Improving System Efficiency
Describe a situation where you worked on improving response time and system efficiency significantly.
- 02
Peer/Leadership Recognition
Describe a project or moment where you were regarded exceptionally well by peers or leadership.
Paytm other questions
- 01
Spring Transactional Behavior
Explain what the provided Spring service code does, how the @Transactional annotation behaves, and what gets committed or rolled back when an exception occurs. java @Service public class OrderService { @Transactional public void placeOrder() { saveOrder();…
- 02
Code Review and Optimization
Given a code snippet Asked to identify: Logical issues Concurrency or reliability problems Possible improvements
- 03
Injecting Request-Scoped Bean into Singleton in Spring Boot
Why does injecting a @RequestScope bean into a singleton fail in Spring Boot?
- 04
Role of @RefreshScope in Spring Cloud
What is the role of @RefreshScope in dynamic configuration updates?
Paytm interview questions FAQ
What questions are asked in Paytm interviews?
Candidates reported 52 distinct questions across 15 Paytm interviews. 25 coding and DSA questions, 21 system design questions, 2 behavioural and HR questions, 4 other questions.
Which Paytm interview questions are asked most often?
The most repeated are "Rotten Oranges" (2 times).
How difficult are Paytm interview questions?
Of the questions candidates rated, 7% were easy, 53% medium and 40% hard.