BillDesk Senior Software Engineer Interview Questions and Answers

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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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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Hackerrank questions

Q1. Coding through screen sharing
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Q1. Discussion on previous projects
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Q1. Behavioural analysis
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Q1. Behavioural questions and discussions
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Questions on alogirithm analysis

Data structures and algo. 2 ques were asked in hackerrank

Q1. Questions related to System design
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Q1. Basic question related to Spring and Java
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Q1. Design Rate Limiter LLD
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Q2. What are SOLID Principles? Springboot questions
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Q1. Hashing based questions using maps
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Q1. Explain Concurrency
Ans. 
Concurrency is the ability of a system to execute multiple tasks simultaneously.
• Concurrency allows multiple tasks to run concurrently, improving performance and efficiency.

• Concurrency can be achieved through multithreading or multiprocessing.

• Example: A web server handling multiple requests simultaneously using multithreading.
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Q2. Explain Acid principles
Ans. 
ACID principles are a set of properties that guarantee database transactions are processed reliably.
• Atomicity: Transactions are all or nothing. If one part of the transaction fails, the entire transaction is rolled back.

• Consistency: Transactions bring the database from one valid state to another. All constraints are satisfied.

• Isolation: Transactions are isolated from each other until they are completed.

• Durability: Once...read more
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