Epsilon Senior Software Engineer Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Medium

This round consisted of questions from DS/Algo , OOPS and Operating Systems primarily usage of some basic UNIX commands .

Q1. 
Kth Largest Number Problem Statement
You are given a continuous stream of numbers, and the task is to determine the kth largest number at any moment during the stream.
Explanation:
A specialized data st...read more
Ans. 
Design a data structure to find the kth largest number in a continuous stream of integers.
• Design a specialized data structure to handle an indefinite number of integers from the stream.

• Implement 'add(DATA)' to incorporate integers into the stream's pool.

• Implement 'getKthLargest()' to retrieve the kth largest number from the pool.

• Maintain the pool of numbers and return the kth largest number for each query.

• Ensure effici
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Q2. What is an interface?
Ans. 
An interface in software engineering is a contract that defines the methods that a class must implement.
• Defines a set of methods that a class must implement

• Provides a way to achieve abstraction and multiple inheritance

• Helps in achieving loose coupling between classes
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Q3. Can you explain the SOLID principles in Object-Oriented Design?
Ans. 
SOLID principles are a set of five design principles in object-oriented programming to make software designs more understandable, flexible, and maintainable.
• S - Single Responsibility Principle: A class should have only one reason to change.

• O - Open/Closed Principle: Software entities should be open for extension but closed for modification.

• L - Liskov Substitution Principle: Objects of a superclass should be replaceable...read more
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Q4. Can you explain piping in Unix/Linux?
Ans. 
Piping in Unix/Linux allows the output of one command to be used as the input for another command.
• Piping is done using the '|' symbol

• It helps in connecting multiple commands together to perform complex operations

• Example: ls -l | grep 'txt' - This command lists all files in long format and then filters for files with 'txt' in their name
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Round duration - 60 Minutes
Round difficulty - Medium

This round had questions revolving around OS , Selenium and some common concepts from DBMS. The interviewer was quite experienced and made the whole interview quite wholesome for me.

Q1. Can you explain any 5 essential UNIX commands?
Ans. 
Essential UNIX commands include ls, cd, pwd, mkdir, and rm.
• ls - list directory contents

• cd - change directory

• pwd - print working directory

• mkdir - make directory

• rm - remove files or directories
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Q2. How do you enable Actuator in a Spring Boot application?
Ans. 
To enable Actuator in a Spring Boot application, you need to include the Actuator dependency in your pom.xml file and configure it in the application.properties file.
• Include Actuator dependency in pom.xml file

• Configure Actuator endpoints in application.properties file

• Access Actuator endpoints to monitor and manage the application
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Q3. What is dependency injection?
Ans. 
Dependency injection is a design pattern in which components are given their dependencies rather than creating them internally.
• Allows for easier testing by providing mock dependencies

• Promotes loose coupling between components

• Improves code reusability and maintainability

• Examples: Constructor injection, Setter injection, Interface injection
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Q4. What are Self-Join and Cross-Join in the context of database management systems?
Ans. 
Self-Join is when a table is joined with itself, while Cross-Join is when every row from one table is combined with every row from another table.
• Self-Join is used to combine rows with other rows in the same table.

• Cross-Join generates a Cartesian product of the two tables involved.

• Self-Join is typically used to compare rows within the same table, like in hierarchical structures.

• Cross-Join is used when there is no common
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Q5. What are views in SQL?
Ans. 
Views in SQL are virtual tables that are generated based on the result set of a SELECT query.
• Views are saved SELECT queries that can be treated as tables.

• They can simplify complex queries by storing them as a view.

• Views do not store data themselves, but display data from the underlying tables.

• They can be used to restrict access to specific columns or rows of a table.

• Views can be used for data abstraction and security p
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Round duration - 30 Minutes
Round difficulty - Easy

This is a cultural fitment testing round .HR was very frank and asked standard questions. Then we discussed about my role.

Q1. Why should we hire you?
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Q2. Why are you looking for a job change?
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