PayU Payments Senior Software Engineer Interview Questions and Answers

Q1. System Design for Task Scheduler
Ans. 
Design a scalable task scheduler to manage and execute tasks efficiently based on priority and timing.
• Define task attributes: ID, priority, execution time, and status.

• Use a priority queue to manage task scheduling based on priority.

• Implement worker threads to execute tasks concurrently.

• Consider persistent storage for tasks to survive system restarts.

• Provide an API for adding, updating, and removing tasks.
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Q2. Past work experience
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I have extensive experience in software development, focusing on scalable applications and team collaboration.
• Led a team of 5 developers in creating a microservices architecture for a healthcare application, improving scalability by 40%.

• Implemented CI/CD pipelines using Jenkins and Docker, reducing deployment time from hours to minutes.

• Collaborated with cross-functional teams to gather requirements and deliver features...read more
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Q1. Low Level Design: How to do rate limiting for a platform serving 100K requests per second.
Ans. 
Implement rate limiting for a platform serving 100K requests per second.
• Use a token bucket algorithm to limit the rate of incoming requests.

• Set a maximum number of tokens in the bucket to control the rate.

• Refill the bucket at a constant rate to allow bursts of requests.

• Track the timestamp of the last request to enforce the rate limit.

• Consider using a distributed rate limiting system for scalability.

• Monitor and adjust t...read more
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Q1. Explain the last technically challenging topic that you have worked on. The engineering manager is only interested in self boasting. Without even trying to understand the entire problem statement, they try...read more
Ans. 
I recently tackled the challenge of optimizing a microservices architecture for a high-traffic e-commerce platform.
• Implemented service mesh using Istio to manage microservices communication and enhance observability.

• Refactored legacy monolithic components into smaller, independent services, improving deployment speed.

• Utilized Kubernetes for orchestration, enabling auto-scaling based on traffic patterns, which improved ...read more
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I was asked two DSA questions and duration was of one hour.
1. Calculate Sum of edges of LinkedList
2. Given a list of numbers, find out all the pythagorean triplets.

This was also a DSA round for 1 hour and expected to solve two problems (Medium)

This was a system design round for one hour

Q1. In memory sql db
Ans. 
In-memory SQL databases store data in memory for faster access and processing.
• In-memory databases keep all data in RAM for quicker retrieval compared to disk-based databases.

• Examples include SQLite in-memory database and Redis.

• They are commonly used for caching, real-time analytics, and temporary data storage.
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Q1. Design review management system
Ans. 
A design review management system streamlines the process of reviewing and approving design documents and artifacts.
• User roles: Define roles such as reviewers, designers, and admins to manage permissions.

• Workflow: Implement a clear workflow for submitting, reviewing, and approving designs.

• Version control: Track changes in design documents to maintain a history of revisions.

• Notifications: Send alerts to reviewers when n...read more
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Q2. How can we add state in the above question
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State management in React allows components to maintain and update their own data, enhancing interactivity and user experience.
• Local State: Each component can have its own state using the useState hook, allowing for dynamic updates. Example: A counter component that increments a value.

• Global State: For shared state across multiple components, use Context API or libraries like Redux. Example: User authentication status ...read more
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