PayMate India Assistant System Engineer Trainee Interview Questions and Answers

You should be familiar with core java features. Collections, converting one collection Array / Vector to other. Removing duplicates. Lambda chaining / Functional programming. Basic SQL - Joins, Aggregates etc.

Q1. Explain Architecture of applications you worked on. Justify use of components. System Design questions.
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It was about DS Algo and Java garbage collection,multithreading

Q1. Low level design of rate limiter
Ans. 
Rate limiter is a system that controls the rate of traffic sent or received by a network interface.
• Implement a token bucket algorithm to track and limit the rate of requests

• Use a sliding window algorithm to track the number of requests within a specific time frame

• Consider using a distributed rate limiter for scalability and fault tolerance
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Q2. Springboot basics, java basics, future interfaces, basic sql queries
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Round duration - 90 minutes
Round difficulty - Medium

Contained mix of coding, oops and general programming questions

Coding was live coding round
It was around 12pm
They used their own coding environment, I coded in java

Q1. 
Maximum Subarray Sum Problem Statement
Given an array arr of length N consisting of integers, find the sum of the subarray (including empty subarray) with the maximum sum among all subarrays.
Explanation...read more
Ans. 
Find the sum of the subarray with the maximum sum among all subarrays in an array of integers.
• Iterate through the array and keep track of the maximum sum subarray seen so far.

• Use Kadane's algorithm to efficiently find the maximum subarray sum.

• Consider the case where all elements in the array are negative.

• Handle the case where the array contains only one element.
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Round duration - 90 Minutes
Round difficulty - Hard

It was a collection of HLD AND LLD
Was around 12pm
This was conducted on bluejeans

Q1. Design a URL shortener with a database and all necessary components.
Ans. 
Design a URL shortener with database and necessary components
• Use a unique identifier for each URL to generate short links

• Store the original URL and corresponding short link in a database

• Implement a redirect mechanism to redirect short links to original URLs

• Consider implementing analytics to track usage and performance

• Ensure scalability and reliability of the system
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Round duration - 60 Minutes
Round difficulty - Easy

It was a friendly managerial round with director of my team, he was very for me to come on board and explained truthfully how payu is.

Round duration - 30 Minutes
Round difficulty - Easy

Just a normal HR discussion, he informed me that I've been selected and we discussed about the salary part

Q1. Can you describe your experience working in a corporate environment?
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Q1. Number of subset
Ans. 
Calculate the number of subsets of a given set
• The number of subsets of a set with n elements is 2^n

• Include the empty set and the set itself in the count

• For example, a set with 3 elements will have 2^3 = 8 subsets
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Q2. Remove kth node from end
Ans. 
Remove the kth node from the end of a linked list.
• Use two pointers, one to traverse the list and another to keep track of the kth node from the end.

• Once the first pointer reaches the end, the second pointer will be at the kth node from the end.

• Adjust the pointers to remove the kth node.
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Q1. Whatsapp low level design
Ans. 
Whatsapp low level design involves messaging, encryption, media sharing, and user authentication.
• Use end-to-end encryption to secure messages

• Implement message queues for real-time message delivery

• Allow media sharing through file transfer protocols

• Use OAuth for user authentication and authorization
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Q2. Lru implemention
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Q1. Longest Consecutive Sequence
Ans. 
Find the length of the longest consecutive elements sequence in an array.
• Sort the array to ensure consecutive elements are adjacent

• Iterate through the array and keep track of the current consecutive sequence length

• Update the longest consecutive sequence length as you iterate
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Q2. Core Java Questions
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Q1. Executor Service and it's code
Ans. 
Executor Service is a framework provided by Java for managing and executing asynchronous tasks.
• Executor Service allows you to easily create and manage threads for executing tasks.

• It provides a way to control the number of threads used for executing tasks, which can help prevent resource exhaustion.

• You can submit tasks to an Executor Service using methods like execute() or submit().

• Executor Service can be used to execut...read more
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Q2. Core Java and Spring boot questions
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Q1. Design patterns
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Q2. Core Java questions
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A coding test based on data structure and Algorithms.

Q1. Question based on Projects in the resume
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Q2. Data Structure and Algorithms Object oriented programming Database management system Operating system
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The Question was average, the interviewer had a fixed approach in mind, which he wanted to follow, but was friendly and trying to help. Overall a good experience.

There was a Hackerearth test with two questions

Q1. Some standard data structures question on array
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Q2. Standard question on trees
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