PayMate India Assistant System Engineer 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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Q1. Questions based on DSA
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Q1. Java specific Interview
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Q1. Hiring Manager Interview
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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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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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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.

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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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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Round duration - 60 Minutes
Round difficulty - Medium

Time - afternoon. 
Interviewer jumped straight into interview, formal and comfortable environment. 
1. Interviewer introduction 
2. Interviewee introduction
3. Coding question 1 - difficulty medium, topic - arrays
- explain approach, write code (pseudo code is fine), dry run on given TCS. 
4. Coding question 2 - same as above, only question was different. Slightly more difficult but on arrays only. 
5. Questions on Python & Django - difficulty medium - write code related to queryset on django objects
6. SQL question to code - 10th highest salary.

Q1. 
Reverse Only Letters Problem Statement
You are given a string S. The task is to reverse the letters of the string while keeping non-alphabet characters in their original position.
Example:
Input:
S = "...read more
Ans. 
Reverse the letters of a string while keeping non-alphabet characters in their original position.
• Iterate through the string and store the non-alphabet characters in their original positions

• Reverse the letters of the string using two pointers technique

• Combine the reversed letters with the non-alphabet characters to get the final reversed string
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Q2. 
Alternate Positive and Negative Numbers
Given an array arr that contains an equal number of positive and negative elements, rearrange the given array such that positive and negative numbers are arranged a...read more
Ans. 
Rearrange an array with equal positive and negative numbers alternatively while maintaining relative order.
• Iterate through the array and separate positive and negative numbers into two separate arrays.

• Merge the two arrays alternatively into the original array.

• Ensure the relative order of positive and negative numbers is maintained.
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Round duration - 60 Minutes
Round difficulty - Medium

1. Intro of interviewer
2. Intro of interviewee
3. Questions on Python - decorators, static method, class methods
4. Principal of coding, best practices
5. Question on DB - What is indexing, how to improve, best use of indexing.
6. Questions on django - what is django ORM, What is sandbox, Django models, Django queries.
7. Previous job, what do you do, stack you work on.

Very friendly environment, very pleasing person, loved it.