PayPay Corporation Backend Developer Interview Questions and Answers

Q1. What is websocket
Ans. 
WebSocket is a protocol for full-duplex communication channels over a single TCP connection, enabling real-time data exchange.
• WebSocket allows persistent connections, reducing latency compared to traditional HTTP requests.

• It is commonly used in applications like chat apps, online gaming, and live notifications.

• WebSocket connections start with an HTTP handshake, then upgrade to a WebSocket connection.

• Example: A stock tr...read more
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Q2. How to logout application only if logout button is clicked or user leaves site
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Q1. About current project , oops concepts, solid principles, java 8 coding questions
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Q2. Hashmap , hashmap internal implementation
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Q1. Introduce yourself
Ans. 
I am a passionate Backend Developer with 5 years of experience in building scalable and efficient web applications.
• 5 years of experience in backend development

• Proficient in programming languages like Java, Python, and Node.js

• Strong understanding of database management systems such as MySQL and MongoDB

• Experience in developing RESTful APIs and microservices

• Familiar with cloud technologies like AWS and Azure
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Q2. Some python programs
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Standard tcs aptitude tests conducted in college

2 code to be done with test cases

Q1. Explain project done for college final.
Ans. 
Developed a web-based project management system for tracking tasks and deadlines.
• Used PHP and MySQL for backend development

• Implemented user authentication and authorization

• Designed a responsive user interface using HTML, CSS, and JavaScript
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Q2. Python basics and coding with exception
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Q1. Why did you choose the flask over the django and fastapi?
Ans. 
I chose Flask over Django and FastAPI due to its simplicity, flexibility, and ease of use for smaller projects.
• Flask is lightweight and minimalistic, making it easier to set up and use for smaller projects.

• Flask allows for more flexibility in terms of project structure and customization compared to Django.

• Flask is well-suited for rapid prototyping and smaller applications where simplicity is key.

• Django, on the other ha...read more
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Q2. Write the code for flask request and response block?
Ans. 
Flask request and response block code snippet
• Use Flask's request object to access incoming request data

• Use Flask's jsonify function to create a JSON response

• Handle different HTTP methods like GET, POST, etc. in the route function
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Q1. What is ORM? which ORM tool, have you used?
Ans. 
ORM stands for Object-Relational Mapping, a programming technique for converting data between incompatible type systems in object-oriented programming languages.
• ORM is used to map objects from an application to tables in a relational database.

• It simplifies data manipulation by allowing developers to work with objects instead of SQL queries.

• Popular ORM tools include Hibernate for Java, Entity Framework for .NET, and Seq
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Q2. Write ORM code for select item from table?
Ans. 
Use ORM code to select item from a table in database.
• Use ORM query methods like find(), findOne(), or where() to select items from a table.

• Specify the table name and any conditions for the selection.

• Example: User.find({ where: { id: 1 } }) will select a user with id 1 from the User table.
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Q1. Nodejs promises async await difference
Ans. 
Node.js promises are a way to handle asynchronous operations, while async/await is a syntax for writing asynchronous code in a synchronous manner.
• Promises are objects that represent the eventual completion (or failure) of an asynchronous operation.

• Async/await is a syntactic sugar built on top of promises, making asynchronous code look more like synchronous code.

• Async functions return a promise, which allows you to use ...read more
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Q2. Nodejs architecture eventloop
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