CARS24 Senior Software Engineer Interview Questions and Answers for Experienced

Q1. Create a controller , service and repository methods and classes to save userDeatils in table using Spring Data JPA .
Ans. 
Create a controller, service, and repository to save user details using Spring Data JPA.
• Create a UserController class with appropriate mappings for saving user details.

• Create a UserService class with a method to save user details.

• Create a UserRepository interface that extends JpaRepository to handle database operations.

• Implement the saveUserDetails method in the UserService class to call the save method of the UserRepo...read more
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Q1. What is event loop, how it works.
Ans. 
Event loop is a mechanism in programming that allows for asynchronous execution of code by continuously checking for and handling events.
• Event loop is commonly used in JavaScript to handle asynchronous operations like setTimeout, setInterval, and AJAX requests.

• It works by continuously checking the event queue for any pending events, executing them one by one, and then moving on to the next event.

• Event loop helps in pre...read more
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Q2. Micro task queue and macro task queue.
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Q3. Is node.js single threaded or multi-threaded, also discuss threadpool and it's usages.
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Q4. Tell the order of output, among process, promise, setTimeout, fs, setInterval.
Ans. 
The order of output is fs, process, setTimeout, setInterval, promise.
• fs module is synchronous and will output first

• process is next in line

• setTimeout will be executed after process

• setInterval will be executed after setTimeout

• promise will be executed last
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Q1. JavaScript usages compiler or interpreter.
Ans. 
JavaScript is an interpreted language.
• JavaScript is an interpreted language, meaning it is executed line by line at runtime.

• There is no separate compilation step in JavaScript like in languages that use compilers.

• Examples of interpreted languages include Python, Ruby, and PHP.
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Q2. Tell the output among various for loops using var, let and bind.
Ans. 
Output comparison of for loops using var, let, and bind in JavaScript.
• Using var: variable is function-scoped, may lead to unexpected behavior in loops.

• Using let: variable is block-scoped, recommended for loop iterations.

• Using bind: creates a new function with a specified 'this' value and initial arguments.
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Q3. A medium level dsa question on array, solved it using pre-sum.
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Q4. Situation based question, on how to pick a suitable database.
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Q1. What do you do on daily basis, and how to decide a tech-stack on high level.
Ans. 
I work on coding, debugging, testing, and collaborating with team members. Tech stack decisions are based on project requirements, scalability, performance, and team expertise.
• Daily tasks include coding, debugging, testing, and collaborating with team members

• Tech stack decisions are based on project requirements, scalability, performance, and team expertise

• Consider factors like language compatibility, libraries/framewo...read more
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Q2. Design an online scalable, real-time document sharing application like google docs.
Ans. 
Design a scalable, real-time document sharing app like Google Docs.
• Use websockets for real-time collaboration

• Implement version control to track changes

• Utilize a distributed database for scalability

• Include user authentication and access control

• Support offline editing with automatic sync
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Q3. How to handle images also in the future.
Ans. 
Utilize cloud storage for scalability, implement image compression techniques, and regularly update image processing libraries.
• Utilize cloud storage for scalability

• Implement image compression techniques

• Regularly update image processing libraries
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Q4. Any other way to solve the problem, of high I/O on same document to overcome throughput and conflicts.
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Q1. Template and Reactive Forms in Angular
Ans. 
Template and Reactive Forms in Angular are two ways to handle forms in Angular applications.
• Template Forms are based on the traditional HTML forms and are easy to use for simple forms.

• Reactive Forms are more flexible and powerful, allowing for complex form validation and dynamic form controls.

• Template Forms use two-way data binding, while Reactive Forms use a more reactive approach with observables.

• Reactive Forms are r...read more
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Questions were crayon box ,the bot and the game and happy neighbourhood for 90 mins

Q1. Array basics was asked
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Q2. Segment tree,prefix sum
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Q1. Low level design was asked
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I was asked question on sliding window on finding the largest subarray with all distinct numbers. The interviewer was very helpful.

Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
0/1 Knapsack Problem Statement
A thief is planning to rob a store and can carry a maximum weight of 'W' in his knapsack. The store contains 'N' items where the ith item has a weight of 'wi' and a value of...read more
Ans. 
Yes, the 0/1 Knapsack problem can be solved using dynamic programming with a space complexity of not more than O(W).
• Use a 1D array to store the maximum value that can be stolen for each weight capacity from 0 to W.

• Iterate through each item and update the array based on whether including the item would increase the total value.

• The final value in the array at index W will be the maximum value that can be stolen.
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Q2. 
Find the Second Largest Element
Given an array or list of integers 'ARR', identify the second largest element in 'ARR'.
If a second largest element does not exist, return -1.
Example:
Input:
ARR = [2,...read more
Ans. 
Find the second largest element in an array of integers.
• Iterate through the array to find the largest and second largest elements.

• Handle cases where all elements are identical.

• Return -1 if a second largest element does not exist.
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Round duration - 60 Minutes
Round difficulty - Easy

System Design Round

Q1. Design a system for Twitter, discussing its architecture, key components, and scalability considerations.
Ans. 
Design a scalable system for Twitter with key components and architecture.
• Use microservices architecture for scalability and fault isolation.

• Key components include user service, tweet service, timeline service, and notification service.

• Use a distributed database like Cassandra for storing tweets and user data.

• Implement a message queue like Kafka for handling real-time updates and notifications.

• Use a caching layer like ...read more
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Round duration - 30 Minutes
Round difficulty - Easy

It is just a formality

Round duration - 60 minutes
Round difficulty - Easy

The round consisted of 2 coding Problems and it lasted for 60 minutes from 12:00 PM to 1:00 PM on Hackerearth.
Use of other IDEs was prohibited and video was on.

Q1. 
Implement indexOf Function
You are provided with two strings A and B. Your task is to find the index of the first occurrence of A within B. If A is not found in B, return -1.
Example:
Input:
A = "bc", ...read more
Ans. 
Implement a function to find the index of the first occurrence of one string within another string.
• Iterate through the second string and check if a substring of the same length as the first string matches the first string.

• Return the index of the first occurrence of the first string within the second string, or -1 if not found.

• Handle edge cases like empty strings or when the first string is longer than the second string
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Q2. 
Problem: Search In Rotated Sorted Array
Given a sorted array that has been rotated clockwise by an unknown amount, you need to answer Q queries. Each query is represented by an integer Q[i], and you must ...read more
Ans. 
Search for integers in a rotated sorted array efficiently.
• Implement binary search to find the target integer in the rotated array.

• Handle the rotation by checking which side of the array is sorted before performing binary search.

• Return the index of the target integer if found, else return -1.

• Time complexity of O(logN) is required for each query.
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Round duration - 60 minutes
Round difficulty - Medium

The round was conducted on Google Meet with 2 interviewers . They were friendly and helpful.
The timing was 12:00 to 1:00 PM.
Our Video was on .

Q1. 
Distinct Subsequences Problem Statement
You are given a string 'S' of length 'N' which may include duplicate alphabets. Your goal is to calculate the number of distinct subsequences in the string.
Exampl...read more
Ans. 
Calculate the number of distinct subsequences in a string with possible duplicates.
• Use dynamic programming to keep track of the count of distinct subsequences for each character in the string.

• Consider the cases where the current character is included or excluded in the subsequence.

• Handle duplicates by considering the previous occurrence of the character.

• Return the count of distinct subsequences modulo 10^9 + 7.
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Round duration - 60 minutes
Round difficulty - Easy

This was a Behavioral Round. It lasted for 45-50 minutes. It consisted of a discussion on my projects. The interviewer was very impressed by the way I explained my projects. She even appreciated me for that. This was followed by normal HR questions .Timing of This round was 4:00 PM to 5:00 PM