Deliveroo Software Engineer II Interview Questions and Answers

Q1. Asked to write a program to check whether string is valid or not. String consists of only three kind of special characters "(), [], {}". We need to return true if all special characters are in correct for...read more
Add your answer
Q2. What is useRef hook used for?
Ans. 
useRef hook is used to persist a mutable value across renders without causing a re-render.
• Used to store mutable values that do not trigger re-renders.

• Commonly used for accessing DOM elements or storing previous values.

• Does not cause a re-render when the value changes.
Answered by AI
Add your answer
Q3. What are the best practices to avoid rerenders and to improve performance
Ans. 
Use memoization, virtual DOM, and shouldComponentUpdate to avoid unnecessary rerenders and improve performance.
• Implement memoization to store the result of expensive function calls and avoid recalculating them.

• Use virtual DOM to efficiently update only the parts of the UI that have changed.

• Override shouldComponentUpdate to prevent unnecessary rerenders by comparing current and next props/state.
Answered by AI
Add your answer
Q4. What are callbacks, Promises, async await
Ans. 
Callbacks, Promises, async await are asynchronous programming concepts in JavaScript.
• Callbacks are functions passed as arguments to another function to be executed later.

• Promises are objects representing the eventual completion or failure of an asynchronous operation.

• async await is a syntax for writing asynchronous code that looks synchronous, making it easier to read and maintain.

• Example: Using a callback to handle th...read more
Answered by AI
Add your answer

It was an online assessment. Some coding questions. Some cs fundamental mcqs. SQL query, Rest Api question.

An assignment to create a game using nodejs/ go lang/ java.

Q1. Discussion related to Assignment. Told some changes and told to add some more functionalities.
Add your answer
Q2. Some APIS were given. It was case study. You had to show the dishes to a customer according to his preferences.
Add your answer

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
Answered by AI
Add your answer
Q2. Micro task queue and macro task queue.
Add your answer
Q3. Is node.js single threaded or multi-threaded, also discuss threadpool and it's usages.
Add your answer
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
Answered by AI
Add your answer

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.
Answered by AI
Add your answer
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.
Answered by AI
Add your answer
Q3. A medium level dsa question on array, solved it using pre-sum.
Add your answer
Q4. Situation based question, on how to pick a suitable database.
Add your answer

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
Answered by AI
Add your answer
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
Answered by AI
Add your answer
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
Answered by AI
Add your answer
Q4. Any other way to solve the problem, of high I/O on same document to overcome throughput and conflicts.
Add your answer

Questions were crayon box ,the bot and the game and happy neighbourhood for 90 mins

Q1. Array basics was asked
Add your answer
Q2. Segment tree,prefix sum
Add your answer

Q1. Low level design was asked
Add your answer

3 questions easy-medium level leetcode problem I solved 2 completely and 3rd question partially (9/15 test cases passed) to move on to 2nd round

Q1. Implement an app similar to splitwise
Add your answer

Q1. Create pagination component using an api show the data for the pages
Ans. 
Create a pagination component using an API to display data for different pages.
• Use API to fetch data for each page

• Implement pagination logic to display data for each page

• Allow users to navigate between pages
Answered by AI
Add your answer

Q1. He asked to invert a binary tree
Add your answer
Q2. Deep dive in projects
Add your answer
Q3. Asked me indept js questions
Add your answer