Airpay Payment Services Senior Software Engineer Interview Questions and Answers

Q1. Abstract and interface difference
Ans. 
Abstract classes are classes that cannot be instantiated and can have both abstract and non-abstract methods. Interfaces are a collection of abstract methods.
• Abstract classes can have constructors, interfaces cannot

• A class can implement multiple interfaces, but can only inherit from one abstract class

• Interfaces can be used to achieve multiple inheritance in Java

• Abstract classes can have instance variables, interfaces c...read more
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Q2. Current project
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I am currently working on a project to develop a web-based inventory management system.
• Developing a user-friendly interface for managing inventory

• Implementing database functionality to store and retrieve inventory data

• Integrating with other systems to automate inventory updates

• Creating reports and analytics to track inventory levels and trends
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Sort array without using any inbuilt method?

Q1. Normal java and sql question
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Q1. Sping boot and microservice
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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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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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Machine coding round where SOLID principles are evaluated for real life use case

Machine coding round.

Q1. Algorithm to calculate top k flight from source to destinaton.
Ans. 
Use Dijkstra's algorithm to find the top k shortest paths from source to destination.
• Implement Dijkstra's algorithm to find the shortest paths from source to all other nodes.

• Store the top k shortest paths found in a priority queue or heap.

• Return the top k shortest paths as the result.
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Hacker rank test - 2 medium questions

Q1. Create and implement product management system with APIs and test case
Ans. 
Design and implement a product management system with APIs and test cases
• Create a database schema to store product information

• Develop RESTful APIs for CRUD operations on products

• Implement authentication and authorization for API access

• Write unit tests and integration tests for APIs

• Use tools like Postman for API testing
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Q1. Low level design - parking lot
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Q1. High level design - streaming platform
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Q1. Basic questions on past experiences, projects and scenario based questions on how will you handle this and that
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Two sum related problem and advanced Priority Queue related questions

Q1. LLD and class diagram for Minesweeper game
Ans. 
LLD and class diagram for Minesweeper game
• Create classes for Board, Cell, Game, Player

• Use composition to represent relationships between classes

• Implement methods for revealing cells, flagging cells, checking for game over

• Consider using enums for cell states (covered, uncovered, flagged)

• Use UML notation to draw class diagram
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