Classplus Software Engineer Interview Questions and Answers

Low level Design Problem in Java

Q1. Data Structures - Graph Problem DFS
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System Design with few details

Aptitude Test with 1 coding question and 8 other aptitude questions

Q1. DSA questions with some dbms questions.
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Q1. DSA + SQL query writing questions. Do revise SQL before interview.
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As usual interview with an aptitude test

Q1. Two coding questions
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Q2. Two puzzle and iq
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Q1. Subject and project
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Q2. Puzzle and iq test
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Q1. Discuss the project you are most proud of
Ans. 
Developed a mobile app for tracking personal fitness goals
• Used React Native to create a cross-platform app

• Implemented features such as goal setting, progress tracking, and workout logging

• Integrated with wearable devices like Fitbit for automatic data syncing
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Q2. What are ways to speed up SQL queries? List them in increasing order of complexity?
Ans. 
Ways to speed up SQL queries in increasing order of complexity
• Use indexes on columns frequently used in WHERE clauses

• Optimize queries by avoiding unnecessary joins and subqueries

• Use stored procedures to reduce network traffic and improve performance

• Consider denormalizing tables for frequently accessed data

• Use query optimization techniques like query caching and query hints
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Q3. Is Redis single-threaded or multi-threaded?
Ans. 
Redis is single-threaded.
• Redis is single-threaded, meaning it can only execute one command at a time.

• This design choice allows Redis to be extremely fast and efficient for certain use cases.

• However, it also means that Redis may not be the best choice for highly concurrent workloads.
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Q4. What sort of data types can be used as keys in Python?
Ans. 
Data types that can be used as keys in Python include strings, integers, floats, tuples, and custom objects.
• Strings are commonly used as keys in Python dictionaries.

• Integers and floats can also be used as keys.

• Tuples can be used as keys if they only contain immutable elements.

• Custom objects can be used as keys if they are hashable.

• Examples: {'name': 'John'}, {1: 'apple'}, {(1, 2): 'tuple'}
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Q5. What types of indexing exist in SQL?
Ans. 
Types of indexing in SQL include clustered, non-clustered, unique, and composite indexes.
• Clustered index physically reorders the table based on the index key

• Non-clustered index creates a separate structure for the index

• Unique index ensures that all values in the index column are unique

• Composite index uses multiple columns for indexing
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Q1. Scenario based questions to test our experience.
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Q1. Technical questions and puzzles.
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Round duration - 180 minutes
Round difficulty - Hard

The test link had 3 days expiry so I could attempt test anytime. It was conducted on doselect.com

Q1. 
Equilibrium Indices in a Sequence
You are given an array/list named 'SEQUENCE', which consists of 'N' integers. The task is to identify all equilibrium indices in this sequence.
Explanation:
An equilibr...read more
Ans. 
The task is to find the equilibrium indices of a given sequence, where the sum of elements at lower indices is equal to the sum of elements at higher indices.
• Iterate through the sequence and calculate the total sum of all elements

• Initialize a left sum and right sum as 0

• For each index, update the left sum and right sum and check if they are equal

• If they are equal, add the index to the equilibrium indices

• Return the equil
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Round duration - 60 minutes
Round difficulty - Medium

Video interview round wherein I was asked to wrote code for the problem statements given by the interviewer. The problems were mainly focused on advanced JS concepts like asynchonous progamming, timers, closures, and data structure problems around arrays, sets, linked list etc.

Q1. 
Rearrange Linked List Problem Statement
Given a singly linked list in the form 'L1' -> 'L2' -> 'L3' -> ... 'Ln', your task is to rearrange the nodes to the form 'L1' -> 'Ln' -> 'L2' -> '...read more
Ans. 
The task is to rearrange the nodes of a singly linked list in a specific order without altering the data of the nodes.
• Iterate through the linked list to find the middle node using the slow and fast pointer technique.

• Reverse the second half of the linked list.

• Merge the first and reversed second half of the linked list alternatively to get the desired order.
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Round duration - 30 minutes
Round difficulty - Easy

This was the last round with HR wherein they judged cultural fit and there was discussion on things like my expectations v/s their expectations etc.

Round duration - 30 minutes
Round difficulty - Easy

This round mainly consisted of some questions on advanced JS topics like Execution Context, Callback queue, Micro task queue, Promises, etc.

Round duration - 60 minutes
Round difficulty - Medium

This round was more technical compared to the previous one. The interviewer was a senior developer. If questions were not answered, answers would be given/explained.

Q1. What are some aggregate operators in MongoDB?
Ans. 
Aggregate operators in MongoDB are used for data aggregation and manipulation.
• Some aggregate operators in MongoDB include $sum, $avg, $min, $max, $push, $addToSet, $first, $last, $project, $match, $group, $sort, $limit, $skip.

• Example: db.collection.aggregate([{$group: {_id: '$field', total: {$sum: '$value'}}}])
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Round duration - 30 minutes
Round difficulty - Easy

This round was mainly to assess my experience level, roles, and responsibilities from my previous company. Salary negotiations also happened here.

4 Coding Questions Leetcode Level Medium to Hard. Had to solve it within 1.5 hours.

Was able to solve 2 questions - One hard and one Medium. Hadn't enough time to solve all.

Q1. DSA based round. Was asked to write 3 APIs based on the the given n-ary tree.
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Q2. Questions based on Path, end node, best path, etc.
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Q1. System Design round : Was asked to design RDBMS for the given problem.
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Q1. HM Round : Mostly behavioral based around Twilio Magic Values
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Q1. Bar Raiser Round : Taken by a director. Was asked behavioral questions again.
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