PayPal Software Engineer II Interview Questions and Answers for Experienced

First round was screening of resume and few basic coding questions

In second round there is 3 panels at same day for 3 hours one after one all there round are technical and coding interviews level is hard one after another round. Situational questions and current project details in deep. Be prepare for coding.

Q1. Normal discussion in HR Round about company details and salary discussions.
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Q1. What are software development design patterns? Can you explain singleton design pattern and code an example to show that?
Ans. 
Software development design patterns are reusable solutions to common problems encountered in software design.
• Design patterns help in creating maintainable, scalable, and efficient software.

• Singleton design pattern ensures a class has only one instance and provides a global point of access to it.

• Example: Implementing a singleton class in Java -

• public class Singleton { private static Singleton instance; private Singleto...read more
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Q2. Can you develop and simple API app to show its running and anyone request sending to it?
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Q3. What kind of databases you’ve worked on? And explain what is DML!
Ans. 
I have worked on relational databases like MySQL and PostgreSQL. DML stands for Data Manipulation Language.
• Worked on MySQL and PostgreSQL databases

• Familiar with writing SQL queries for data manipulation

• DML stands for Data Manipulation Language
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Q4. When we work with micro services , what is your experience which becomes challenge?
Ans. 
One challenge when working with microservices is managing communication between services.
• Ensuring proper service discovery and registration

• Handling network latency and failures

• Implementing effective monitoring and logging

• Maintaining consistency and data integrity across services
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Q1. What are the types of deployments?
Ans. 
Types of deployments include blue-green, canary, rolling, and immutable.
• Blue-green deployment involves running two identical production environments and switching between them.

• Canary deployment gradually rolls out changes to a small subset of users before deploying to the entire infrastructure.

• Rolling deployment updates a few instances at a time, ensuring continuous availability.

• Immutable deployment creates new instanc
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Q2. What is Blue Green Deployment ?
Ans. 
Blue Green Deployment is a software release strategy that reduces downtime and risk by running two identical production environments.
• In Blue Green Deployment, one environment (blue) is live and serving production traffic while the other (green) is idle and ready to be switched to at any time.

• This strategy allows for zero downtime deployments, as the switch between blue and green environments can be done seamlessly.

• Blue...read more
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Q3. I was asked travelling salesman problem to solve.!
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Q1. Tell me what you liked in last 2 rounds!
Ans. 
I enjoyed the challenging technical questions and the opportunity to showcase my problem-solving skills.
• Challenging technical questions

• Opportunity to showcase problem-solving skills
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Q2. Explain me the best project as per you which you worked upon and features of it.
Ans. 
Developed a web-based project management tool for tracking tasks and deadlines.
• Implemented user authentication and authorization using JWT tokens

• Integrated real-time chat feature using WebSockets

• Utilized React for front-end and Node.js for back-end development
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Q3. Some RegEx related questions were asked.
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Q4. How vector databases work?
Ans. 
Vector databases store data in a vector format, allowing for efficient querying and analysis of high-dimensional data.
• Vector databases use vectors to represent data points in a multi-dimensional space.

• They are commonly used in machine learning and data science applications for tasks like similarity search and clustering.

• Examples of vector databases include Faiss, Annoy, and Milvus.
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Q5. If I give you a coding problem to solve in the language you don’t know, can you solve it, when you’re allowed to refer Google search?
Ans. 
Yes, I can solve a coding problem in a language I don't know with Google search.
• Utilize Google search to understand syntax and concepts in the unfamiliar language

• Break down the problem into smaller parts and search for solutions to each part

• Refer to online resources, forums, and documentation for guidance

• Practice writing and testing code snippets in the new language before attempting the full solution
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Q6. How you can parse location and shop name from a card transaction string?
Ans. 
Use regex to extract location and shop name from transaction string.
• Use regular expressions to match patterns for location and shop name.

• Look for keywords like 'at', 'from', 'in' to identify location.

• Consider variations in transaction strings and account for them in regex patterns.

• Example: 'Spent $50 at Starbucks Coffee' -> Location: Starbucks Coffee, Shop Name: Starbucks Coffee
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Q1. Pl sql Unix api configuration
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Q2. Routing how to use proxy
Ans. 
Routing through a proxy involves configuring the proxy server to forward requests to the destination server.
• Configure the proxy server to listen for incoming requests

• Configure the proxy server to forward requests to the destination server

• Configure the client to use the proxy server for outgoing requests

• Use a proxy server to bypass network restrictions or improve performance

• Examples: Nginx, Apache, Squid
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Hacker rank long coding questions with questions for python,c++,javascript , data bast related questions

Q1. Javascript related some coding questions and some data base related
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Round duration - 45 minutes
Round difficulty - Easy

This was a technical interview round.

Q1. How does AJAX work?
Ans. 
AJAX allows web pages to be updated asynchronously by exchanging data with a web server behind the scenes.
• AJAX stands for Asynchronous JavaScript and XML.

• It allows web pages to update content without reloading the entire page.

• AJAX uses XMLHttpRequest object to send and receive data from a server.

• Commonly used in web applications to provide a more responsive user experience.
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Q2. What is the difference between SOAP and REST?
Ans. 
SOAP is a protocol, while REST is an architectural style for web services.
• SOAP is a protocol that uses XML for message format and relies on a request-response model.

• REST is an architectural style that uses standard HTTP methods like GET, POST, PUT, DELETE.

• SOAP is more rigid and requires more bandwidth, while REST is lightweight and flexible.

• SOAP has built-in security features like WS-Security, while REST relies on exte...read more
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Q3. What is the difference between GET and POST methods in APIs?
Ans. 
GET is used to request data from a server, while POST is used to submit data to a server.
• GET requests data from a specified resource, while POST submits data to be processed to a specified resource.

• GET requests are cached by browsers, while POST requests are not.

• GET requests can be bookmarked and shared, while POST requests cannot.

• GET requests have length restrictions, while POST requests do not.

• Example: Using GET to r...read more
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Q4. What is the Observer Pattern?
Ans. 
The Observer Pattern is a behavioral design pattern where an object (subject) maintains a list of dependents (observers) that are notified of any state changes.
• Allows for one-to-many dependency between objects

• When the subject's state changes, all observers are automatically notified and updated

• Commonly used in event handling systems and GUI frameworks
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Round duration - 40 minutes
Round difficulty - Easy

This was the second technical interview round.

Q1. What is a singleton class?
Ans. 
A singleton class is a class that can only have one instance created throughout the entire application.
• Singleton classes have a private constructor to prevent multiple instances from being created.

• They typically provide a static method to access the single instance.

• Commonly used for logging, database connections, and configuration settings.
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Q2. What is meant by immutability in Java?
Ans. 
Immutability in Java refers to the property of objects whose state cannot be changed once they are created.
• Immutability ensures that once an object is created, its state cannot be modified.

• Immutable objects are thread-safe and can be shared without the risk of data corruption.

• String class in Java is an example of an immutable class.

• To create an immutable class, make the class final, all fields private, and provide only
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Q3. What is dependency injection?
Ans. 
Dependency injection is a design pattern where 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. How do you create an immutable class in Java?
Ans. 
To create an immutable class in Java, make the class final, make all fields private and final, provide only getter methods, and do not provide any setter methods.
• Make the class final to prevent inheritance.

• Make all fields private and final to prevent modification.

• Provide only getter methods to access the fields.

• Do not provide any setter methods to modify the fields.
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Round duration - 30 minutes
Round difficulty - Easy

HR round with typical behavioral problems.