Epsilon Interview Questions, Process, and Tips

Basic aptitude question, 50mins 50Qs

1 easy leetcode problem in 30mins and few MCQs based on SQL and SAS

Q1. Conceptual questions on machine learning and statisitcs
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Q1. Behavioural questions
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Q1. About Experience
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Q2. About salary and carrier opportunities
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Q1. About Oracle Architecture
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Q2. About DR configuration
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Q1. What are fact tables in Database
Ans. 
Fact tables are tables in a database that store quantitative data about a business process or activity.
• Fact tables contain the measurements or metrics of a business process or activity

• They are typically linked to dimension tables through foreign keys

• They are used in data warehousing and business intelligence to analyze and report on business performance

• Examples include sales, inventory, and customer activity data
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Q2. What is the situation where you can avoid creating indexes
Ans. 
Indexes can be avoided when the table is small or when the query is infrequent.
• Small tables can be scanned quickly without the need for an index.

• Queries that are run infrequently may not require an index to be created.

• Indexes can also be avoided when the cost of maintaining them outweighs the benefits.

• Indexes may not be necessary for tables that are used for logging or auditing purposes.
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Q3. Question about left outer join
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Q4. Question about Aggregate functions Avg(age)?
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Q1. Based on resume and experience
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Q1. Project management scenario based questions
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Q1. Cultural fitment and company ethos
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Q1. What is routing? Types of routing
Ans. 
Routing is the process of selecting a path for network traffic to travel from one network to another.
• Routing is done by routers in a network.

• Types of routing include static routing, dynamic routing, and default routing.

• Static routing involves manually configuring the routes.

• Dynamic routing uses protocols to automatically update the routing table.

• Default routing is used when there is no specific route for a packet.

• Examp...read more
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Q2. WebAPI Basic authentication and token-based authentication
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Q3. What is a Factory design pattern? How do you implement that?
Ans. 
Factory design pattern is a creational pattern that provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created.
• Factory pattern is used when we have a superclass with multiple subclasses and based on input, we need to return one of the subclass.

• It provides a way to delegate the instantiation logic to child classes.

• Example: java.util.Calendar, java....read more
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Q4. Explain the current project and architecture
Ans. 
The current project is a web-based e-commerce platform with a microservices architecture.
• The project uses a combination of front-end technologies like React and back-end technologies like Node.js and Java.

• It follows a microservices architecture where different services handle specific functionalities like user management, product catalog, and order processing.

• The services communicate with each other through APIs and me...read more
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Q5. What is dependency injection?
Ans. 
Dependency injection is a design pattern that allows objects to receive dependencies rather than creating them internally.
• Dependency injection helps to decouple components and make them more modular.

• It allows for easier testing and maintenance of code.

• There are three types of dependency injection: constructor injection, setter injection, and interface injection.

• Example: Instead of creating a database connection object ...read more
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Q1. What is caching? Types of caching
Ans. 
Caching is the process of storing frequently accessed data in a temporary storage area for faster access.
• Caching reduces the time and resources required to access data.

• Types of caching include browser caching, server caching, and database caching.

• Browser caching stores web page resources like images, stylesheets, and scripts on the user's device.

• Server caching stores frequently accessed data on the server to reduce dat...read more
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Q2. Difference between web application and web API application
Ans. 
Web application is a complete software program accessed through a web browser, while web API application is a set of programming instructions that allow communication between different software systems.
• Web application is a complete software program accessed through a web browser

• Web API application is a set of programming instructions that allow communication between different software systems

• Web application provides a ...read more
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Q3. What are interfaces? Why do we need them?
Ans. 
Interfaces are contracts that define a set of methods that a class must implement. They help achieve abstraction and loose coupling.
• Interfaces provide a way to achieve abstraction and loose coupling in code.

• They define a set of methods that a class must implement, but not how they are implemented.

• Classes can implement multiple interfaces, allowing for greater flexibility and reusability.

• Interfaces are commonly used in ...read more
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Q4. How to handle load balancing? What is load balancing?
Ans. 
Load balancing is the process of distributing network traffic across multiple servers to avoid overloading a single server.
• Load balancing helps to improve the performance, availability, and scalability of applications.

• It can be achieved through hardware or software solutions.

• Examples of load balancing algorithms include round-robin, least connections, and IP hash.

• Load balancing can also be combined with other technique...read more
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Q5. What is SSL? Why do we need it?
Ans. 
SSL is a security protocol used to establish an encrypted link between a web server and a browser.
• SSL stands for Secure Sockets Layer.

• It is used to protect sensitive information such as login credentials, credit card details, etc.

• SSL uses encryption to ensure that data transmitted between the server and browser cannot be intercepted by third parties.

• It is essential for e-commerce websites, online banking, and any websi...read more
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Q6. What is encryption? How to encrypt/decrypt?
Ans. 
Encryption is the process of converting plain text into a coded message to prevent unauthorized access.
• Encryption uses an algorithm and a key to convert plain text into ciphertext.

• Decryption uses the same algorithm and key to convert ciphertext back into plain text.

• Common encryption algorithms include AES, RSA, and Blowfish.

• Encryption is used to protect sensitive data such as passwords, credit card numbers, and persona...read more
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Q7. What is the CORS issue? Where does it occur?
Ans. 
CORS (Cross-Origin Resource Sharing) is a security feature that restricts web pages from making requests to a different domain.
• CORS issue occurs when a web page tries to access resources from a different domain

• It is a security feature implemented by web browsers to prevent cross-site scripting attacks

• CORS issue can be resolved by configuring the server to allow cross-origin requests or by using JSONP

• It can occur in AJA
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Q8. If we have 2 tables with the same schema, one table has indexes and the other doesn't. Will there be any performance difference on that tables with insert action?
Ans. 
Indexes can slow down insert performance due to the overhead of maintaining the index.
• Inserting data into the table without indexes will be faster than inserting into the table with indexes.

• The more indexes a table has, the slower the insert performance will be.

• However, indexes can improve query performance by allowing the database to quickly find the data being searched for.
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Q9. What are ajax calls?
Ans. 
Ajax calls are asynchronous HTTP requests made by JavaScript to a server without reloading the page.
• Ajax stands for Asynchronous JavaScript and XML

• Used to update parts of a web page without reloading the entire page

• Can be used to fetch data from a server and display it on a web page

• Examples: Google Maps, Facebook News Feed
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Q10. What is angular? Which language does it use? What is typescript?
Ans. 
Angular is a popular front-end web application framework that uses TypeScript as its primary language.
• Angular is developed and maintained by Google.

• It is used for building dynamic, single-page web applications.

• It uses TypeScript, a superset of JavaScript, which adds features like static typing and class-based object-oriented programming.

• Angular provides a range of features like data binding, dependency injection, and c...read more
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Q11. What is lazy loading?
Ans. 
Lazy loading is a technique used to defer the loading of non-critical resources until they are actually needed.
• It improves page load time and performance.

• It reduces the initial load time of a web page.

• It is commonly used for images, videos, and other media files.

• It can be implemented using JavaScript or server-side scripting.

• Example: Images below the fold on a webpage are loaded only when the user scrolls down to them.
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First round was online assessment where Aptitude Questions, Technical MCQs and 2 coding questions were asked. Coding questions level easy

Q1. Write a program to check if a given string can become palindrome if letters are re-arranged
Ans. 
Program to check if a string can be rearranged to form a palindrome
• Create a frequency map of characters in the string

• Count the number of characters with odd frequencies

• If there is at most one character with odd frequency, the string can be rearranged to form a palindrome
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Q2. Different Data types in Python ?
Ans. 
Python supports various data types including integers, floats, strings, lists, tuples, dictionaries, and more.
• Integers: whole numbers without decimal points (e.g. 5, -3)

• Floats: numbers with decimal points (e.g. 3.14, -0.5)

• Strings: sequences of characters enclosed in quotes (e.g. 'hello', '123')

• Lists: ordered collections of items (e.g. [1, 'apple', True])

• Tuples: ordered, immutable collections of items (e.g. (1, 'banana'...read more
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Q3. Some basic probability based questions
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Q1. Explain your project.
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Q2. What is Normalization ?
Ans. 
Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity.
• Normalization is used to eliminate data redundancy by dividing the database into multiple tables and defining relationships between them.

• It helps in reducing data anomalies such as insertion, update, and deletion anomalies.

• Normalization is achieved through a series of stages called normal forms (1NF, 2NF, 3NF, ...read more
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Q3. What is diamond problem in Java?
Ans. 
Diamond problem in Java occurs when a class inherits from two classes that have a common ancestor, resulting in ambiguity.
• Occurs in multiple inheritance when a class inherits from two classes that have a common ancestor

• Results in ambiguity as the compiler cannot determine which method to call

• Can be resolved using interfaces or by explicitly overriding methods
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Q4. What is the differences between Java and Python?
Ans. 
Java is statically typed, object-oriented language with a focus on performance and scalability. Python is dynamically typed, high-level language known for its simplicity and readability.
• Java is statically typed, meaning variable types are explicitly declared at compile time. Python is dynamically typed, allowing for more flexibility but potentially leading to runtime errors.

• Java is more verbose and requires more boiler...read more
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Q5. Latest version of Java
Ans. 
Java 17 is the latest version as of September 2021.
• Java 17 was released on September 14, 2021.

• It includes new features like sealed classes, pattern matching for switch statements, and more.

• Oracle provides long-term support for Java 17 until 2029.
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Q6. Write SQL query to find 2nd largest Number from DB?
Ans. 
Use a subquery to find the 2nd largest number in a database table.
• Use a subquery to select all distinct numbers from the table

• Order the numbers in descending order

• Use LIMIT 1,1 to select the second row which will be the 2nd largest number
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Q1. Who is your Inspiration
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Q2. Why do you want to join Epsilon
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