Volt Senior Software Engineer Interview Questions and Answers

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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Q1. Low Level Design for Chess
Ans. 
Low level design for a chess game including classes, functions, and data structures.
• Create classes for pieces (e.g. Pawn, Rook, Bishop) with properties like position and color

• Implement functions for moving pieces, checking valid moves, and capturing opponent pieces

• Use data structures like 2D arrays to represent the chess board and track piece positions
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Q1. Design Splitwise Application (LLD)
Ans. 
Design a Splitwise application for managing shared expenses among friends.
• Implement user authentication and authorization for secure access.

• Create a user-friendly interface for adding expenses and splitting them among friends.

• Develop algorithms for calculating balances and settling debts between users.

• Include features for adding comments, attaching receipts, and generating reports.

• Consider scalability and performance o...read more
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Q1. 1. Questions around projects : JWT, UserAuthentication etc
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Q2. 2. Write a code to find frequency of characters in a given string?
Ans. 
Code to find frequency of characters in a given string
• Use a hash table to store character frequencies

• Iterate through the string and update the hash table accordingly

• Print the hash table to display the character frequencies
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Q1. 1. Write a code to reverse a linked list?
Ans. 
Code to reverse a linked list
• Create three pointers: prev, curr, and next

• Initialize prev to null and curr to head

• Loop through the list and set next to curr's next node

• Set curr's next node to prev

• Move prev and curr one node ahead

• Return prev as the new head
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Q2. 2. Write a code to reverse linked list in size of K?
Ans. 
Code to reverse linked list in size of K
• Create a function that takes head of linked list and size K as input

• Traverse the linked list in groups of K nodes

• Reverse each group of K nodes using iterative or recursive approach

• Connect the reversed groups to form the final linked list

• Return the new head of the reversed linked list
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Q3. 3. Questions around project and design a database structure for comments system of quora?
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Q1. Basic HR round questions
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Q1. Replace all zeros to 1 which are surrounded by 1's
Ans. 
Replace zeros surrounded by ones with ones in an array of strings
• Iterate through each string in the array

• Check for zeros surrounded by ones and replace them with ones

• Return the modified array of strings
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Q2. Minimum jumps to reach end of an array
Ans. 
The minimum number of jumps needed to reach the end of an array.
• Use dynamic programming to keep track of the minimum jumps needed at each index.

• At each index, calculate the maximum reachable index and update the minimum jumps accordingly.

• Example: For array [2, 3, 1, 1, 2, 4, 2, 0, 1, 1], the minimum jumps needed is 4.
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Q1. LLD Round:- Design classes for bidding system when new bid notifications shown to all users who already bided for it.
Ans. 
Design classes for a bidding system with new bid notifications for users who have already bid.
• Create a Bid class with attributes like bidder, amount, timestamp, etc.

• Create a Notification class with attributes like message, recipient, timestamp, etc.

• Create a BiddingSystem class to manage bids and notifications.

• Implement a method in BiddingSystem to notify users who have already bid when a new bid is placed.

• Consider usin...read more
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Q2. HLD:- Desing Post order service, or last mile like finding rider, notifications etc
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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.