Mobikwik 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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Q1. Number of subset
Ans. 
Calculate the number of subsets of a given set
• The number of subsets of a set with n elements is 2^n

• Include the empty set and the set itself in the count

• For example, a set with 3 elements will have 2^3 = 8 subsets
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Q2. Remove kth node from end
Ans. 
Remove the kth node from the end of a linked list.
• Use two pointers, one to traverse the list and another to keep track of the kth node from the end.

• Once the first pointer reaches the end, the second pointer will be at the kth node from the end.

• Adjust the pointers to remove the kth node.
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Q1. Whatsapp low level design
Ans. 
Whatsapp low level design involves messaging, encryption, media sharing, and user authentication.
• Use end-to-end encryption to secure messages

• Implement message queues for real-time message delivery

• Allow media sharing through file transfer protocols

• Use OAuth for user authentication and authorization
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Q2. Lru implemention
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Q1. Longest Consecutive Sequence
Ans. 
Find the length of the longest consecutive elements sequence in an array.
• Sort the array to ensure consecutive elements are adjacent

• Iterate through the array and keep track of the current consecutive sequence length

• Update the longest consecutive sequence length as you iterate
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Q2. Core Java Questions
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Q1. Executor Service and it's code
Ans. 
Executor Service is a framework provided by Java for managing and executing asynchronous tasks.
• Executor Service allows you to easily create and manage threads for executing tasks.

• It provides a way to control the number of threads used for executing tasks, which can help prevent resource exhaustion.

• You can submit tasks to an Executor Service using methods like execute() or submit().

• Executor Service can be used to execut...read more
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Q2. Core Java and Spring boot questions
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Q1. Design patterns
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Q2. Core Java questions
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Easy Medium questions

Q1. Asked to design Basic Facebook.
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Was a tough oneto crack

Q1. Asked about core Java domain and threds
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Q2. Asked about Java domain and threads collection
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Q3. Threads and collection
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Q1. Deep dive into java concepts. Max diameter of a tree in java.
Ans. 
Max diameter of a tree in Java is the longest path between any two nodes in a tree.
• The diameter of a tree can be calculated by finding the longest path between any two nodes in the tree.

• This can be done by finding the longest path from the root to a leaf node, and then finding the longest path from another leaf node to the root.

• The sum of these two paths gives the diameter of the tree.
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Q1. Lld of loan and borrower design. Design dbs schema. About connection pool, db isolation.
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Q1. Hiring manager round, more about previous experience and some hypothetical questions.
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