Visa Senior Data Scientist Interview Questions and Answers

Q1. Micro services architecture
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Q1. Java ,springboot
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Q1. Springboot and java questions
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Q1. What are SSL certificates?
Ans. 
SSL certificates are digital certificates that authenticate the identity of a website and encrypt information sent to the server.
• SSL certificates ensure secure communication between a user's browser and a website's server.

• They use encryption to protect sensitive data such as login credentials, credit card information, etc.

• SSL certificates are issued by Certificate Authorities (CAs) and contain information about the web...read more
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Q2. What are the ways to secure REST API?
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Securing REST API involves using authentication, authorization, encryption, and input validation.
• Use authentication methods like OAuth, JWT, or API keys to verify the identity of clients.

• Implement authorization to control access to resources based on user roles and permissions.

• Encrypt data transmission using HTTPS to protect sensitive information from being intercepted.

• Validate and sanitize input data to prevent inject
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Q3. What if your application is down for 1 hour in one site in prod?
Ans. 
I would investigate the root cause, work on fixing the issue, and implement measures to prevent it from happening again.
• Investigate the root cause of the downtime, such as network issues, server failures, or software bugs

• Work on fixing the issue promptly to minimize impact on users and business operations

• Implement measures to prevent similar downtime in the future, such as redundancy, monitoring, and failover mechanism
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Q4. How do you make sure a throttling system process dropped messages from a slow downstream service?
Ans. 
Implement a throttling system to handle dropped messages from a slow downstream service.
• Implement a queue to store messages from the downstream service.

• Set a maximum queue size and drop messages when the queue is full.

• Use a timestamp to track when messages were received and process them in order.

• Implement a retry mechanism to reprocess dropped messages after a certain time.

• Monitor the queue size and processing speed to
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Q1. System design basics
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Q2. Java 8 stream api code
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Q3. Current project
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Q1. Only arrogance related stuff
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Q2. Only arrogance related stuff happened
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Java Coding and Data Structure

Q1. Discussion around CV
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Q1. Offer related and work location
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Q2. Nothing specific
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Asked to do coding for RDBMS using any programing language

Q1. Machine coding: Design in-memory document search
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Q1. HLD: Design a ad-click aggregation service
Ans. 
Design an ad-click aggregation service for tracking and analyzing ad clicks.
• Use a distributed system to handle high volume of ad click data

• Implement real-time processing for immediate insights on ad performance

• Utilize a database to store aggregated ad click data for reporting and analysis
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Q1. Design a in-memory cache
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Design a high-performance in-memory cache system for storing and retrieving data efficiently.
• Use a hash table or a key-value store to store data in memory

• Implement caching strategies like LRU (Least Recently Used) or LFU (Least Frequently Used) to manage cache eviction

• Consider using a distributed cache for scalability and fault tolerance

• Optimize cache size and expiration policies based on the application's data access
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Q1. Rating Service Low level design
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