I got referred to DE Shaw by my friend and was invited to take their online coding round.
Round 1 | Online coding | 70 mins:
- Coding section: Don’t remember the exact question but it goes something like this. Given a list of chocolates, their ids, taste values (say X) and some other feature (say Y). You eat one chocolate each day. You eat the chocolate with better taste first. If two chocolates have the same taste, you eat the chocolate with a lower value of Y. Given m queries. Each query contains the day number. For a given day number, you need to print the id of the chocolate that you will eat. [20 mins]
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MCQ section:
- Technical: 10 questions from Data Structures & Algorithms, Operating Systems, DBMS, SQL and Networks. [20 mins]
- Aptitude: 10 questions from Quantitative Aptitude, Problem-solving and Logical & verbal Reasoning. [20 mins]
- 5 questions related to systems. [10 mins]
Round 2 | 1st technical interview | 1.5 hrs:
They told it will be a code pair round so I expected some coding questions. But I was asked a lot of questions from my projects and cs fundamentals.
- I was working on a project which involved multiple users to contribute to a common resource and admins to control them. So, he asked how was it handled and how was an abuse of the feature prevented.
- I was asked a lot of questions from a project that I made with my friends, called Anote-
- What was your contribution? We discussed some features of the project.
- Explain your database design. Then some follow-up questions on the same such as what if I change some part of my collection? Will it work? Why?
- We used a field to optimise the read/delete queries to our database. He asked about this- Why is it used? How did it help to optimise? How did you reach to this solution? etc.
- How does Google web sign-in work? What are JSON Web Tokens(JWT)? Why did you use it? How does it work?
- Suppose you are working on the app and have unsaved progress and the JWT expires (therefore, you can not save the changes to database as the user is not authenticated now), what can you do to prevent loss of data?
- Why did you use Reactjs? How does Reactjs work internally? How does it optimise the speed? etc. (Virtual DOM, Diffing algorithm etc.)
- What is MVC?
- SQL vs NoSQL? What is SQLite?
- What is a Rest API? How is it different from HTTP?
- What are cookies?
- What is an OS?
- What is multiprocessing, multitasking, multi-programming?
- What happens when you start a program in your PC (say, MS Word)?
- What is context switching? What is preemption?
- What is memory hierarchy? What is the need for RAM when secondary memory can also serve its purpose?
- What is a trap? What is an interrupt?
- What is DMA?
- What happens when you type www.google.com in the address bar of your browser?
- What is an IP address?
- What is the OSI model?
- What is OOP?
- Difference between OOP and Functional programming.
- What is an interpreter?
There might be more questions which I don’t remember.
Round 3 | 2nd technical interview | ~1 hour:
- Introduce yourself.
- DE Shaw came to our college two years back for hiring interns and I was rejected in their first round of interview. So, he asked a few questions regarding that.
- How has your understanding of NoSQL databases improved in two years?
- SQL vs NoSQL database? CAP theorem?
- Why did you use Reactjs? How did it help you create better, optimised app efficiently? (Component-based, reusability, virtual DOM, reconciliation etc).
- Why did you use Redux? How does it affect code complexity? How does it improve state management? You can use local storage to store global state, why redux?
- Why did you use a NoSQL database? What were the problems in a relational database that made you use NoSQL?
- Why did you use Nodejs and expressjs?
- What is a Rest API?
- Any idea about how `sudo` works in Linux?
- What happens when you turn on your PC?
- Process of getting the IP address for a given URL?
- Compiler vs interpreter?
There might be more questions which I don’t remember.
Round 4 | 3rd technical interview | ~45 mins:
- Introduce yourself.
- Two years back I was rejected by DE Shaw during their intern hiring process. So he asked- how have you improved in the past two years which proves you are now a good fit for the company?
- He asked about the specs of my PC.
- What do you understand when you say your processor’s speed at 2.7 GHz?
- What do you understand when you say your HDD’s speed is 5400rpm?
- What is SSD? Do you know about a better solution than SSD?
- Suppose, you suddenly notice that your PC is slowing down a lot. What are the possible reasons for this? How will you detect and troubleshoot the problem?
- What is paging? Why is it needed? More questions related to it.
- What is a boot loader? How does dual boot work?
- TCP vs UDP?
- What is an SYN attack?
- Some questions on DNS.
- Switch vs Router?
- Broadcasting vs Multicasting?
- Http vs https? How is https secure?
- What is an API?
- Puzzle: Given 2 identical rectangular pieces. One is iron, other is a magnet. How will you distinguish?
- Puzzle: Given 2 eggs and an n-storey building. Find the lowest floor from where when an egg is thrown, it breaks. Minimise the number of throws.
There might be more questions which I don’t remember.
A few days later, I got a call from HR that they want me to offer a role at DE Shaw & Co and a discussion round was scheduled regarding the same. After which, I accepted the offer.
Few points to note:
- The questions mentioned may miss some follow-ups asked. They were mostly intended to know your depth of knowledge in the topic.
- From my experience, they focus on the projects you have built.
- If you mention something in your resume (especially projects), be confident about every aspect of it. You should know why did you use a tech stack, a library or a framework. You will be asked about it.