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. Does Java support pass by reference?
Ans. 
Yes
• Java uses pass by value for all variables, including object references.

• When an object reference is passed as an argument, a copy of the reference is passed, not the actual object.

• Modifying the reference inside the method will not affect the original reference outside the method.

• However, modifications to the object's state inside the method will be visible outside the method.
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Q2. Explain Singleton Pattern
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Singleton pattern restricts the instantiation of a class to a single object.
• Singleton pattern ensures that only one instance of a class exists throughout the application.

• It provides a global point of access to the instance.

• Commonly used in scenarios where a single instance needs to coordinate actions across the system.

• Example: Database connection manager, logger, configuration manager.
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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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DS, Algo, DP, Greedy, Stack, Heap

Q1. System Design a DropBox
Ans. 
Design a scalable cloud storage system similar to DropBox.
• Use distributed file system for storing files across multiple servers.

• Implement data deduplication to save storage space.

• Use client-side encryption for security.

• Implement file synchronization across devices.

• Utilize load balancing to distribute user requests.

• Implement version control for files.

• Use metadata for efficient file organization.
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Q2. Design a Linked List
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A linked list is a linear data structure where each element is a separate object with a reference to the next element.
• Start with a Node class that has data and a reference to the next node

• Create a LinkedList class that manages the nodes and provides methods like insert, delete, and search

• Example: Node class - data, next; LinkedList class - head, insert(data), delete(data), search(data)
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Q1. About yourself. Projects worked upon
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Q2. Why want to join Ocrolus?
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They have problem of K sorted array and you need to make an sorted array of it.

Q1. Your current job role
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Q2. Software Developer
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Q1. Basic questions on data structures
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Q1. Second round was Managerial Round. The interviewer basically had a conversation with me and asked some hr questions also.
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Q1. Basic HR questions
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It was simple program of url shorting for registered and non registered users each request must have unique shortened url.

Q1. Palindrome implementation and run time
Ans. 
A palindrome is a word or phrase that reads the same backward as forward. Implementing it involves comparing the first and last characters and iterating towards the middle.
• Implement a function that takes a string as input and returns true if it is a palindrome, false otherwise.

• Use two pointers, one starting from the beginning and the other from the end, and compare the characters at each position.

• If the characters matc...read more
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Q2. DSA and various algorithms and run time
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Q1. This round was one on one with VP of engineering. Basic q and a regarding role and responsibilities
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Q1. Relocation, Reason For job change, future plan, careers objective
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