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How To Ace System Design Interview

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Sample Questions Asked In A System Design Interview:

3 Ways to Ace Your System Design Interview
  • Design a chat service like WhatsApp
  • Design a parking lot
  • Design a URL shortener service like TinyURL
  • Design a video streaming service like YouTube/Netflix
  • Design a file sharing service like Google Drive
  • Design a Social Media platform like Instagram, Twitter, or Facebook.

These are some of the popular questions that are asked in this round. As you can see the questions are vague and the problem statement doesn’t provide specific details on what part of the system should be designed.

So, it’s important to know how to approach this round to come up with a good design at the end of this discussion.

What Companies Use System Design Interviews

Below, we’ve compiled a list of our interview guides for every company and role that we’ve covered, where system design interviews are used. This is not a comprehensive list of all companies in the industry that use system design interviews, but it does cover some of the biggest companies in the industry.

If you’d like to learn more about a specific company’s system design interviews, or their overall interview process, then we’d encourage you to check out our guide for that company below :

Top 5 Resources To Prepare For System Design Interview

Staff Software Engineer at Visa

System Design Interview preparation is like never ending story, there is no single source of learning that will give you true sense of confidence or short of completeness. But we cant just keep learning randomly over the internet or Youtube. I have doing research myself from long time and find out if you just learn from these 5 resources, this wont make you master but will give you confidence to crack system design interview. So In this post I am sharing after reading tons of interview experienced shared by selected candidates in top companies on various blogs.

Here are top 5 resources to prepare for System Design Interview.

  • Cracking the coding interview book : Not only this book is very handy for preparing coding interview but also have some fundamental questions about system design. You can check out the system design section of this book. This book have covered frequently asked system design interview questions.
  • Grokking the System Design Interview : Everyone is talking about this course when it comes the starting point for system design interview preparation . This will give you basic foundation about various concepts, topics and how to answer the system design interview questions. The details might be less but flow is very important and this book have covered lot many things in a systematic manner.
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    Design For The Right Scale

    The same feature set requires a very different approach for different scales. Its important to determine the scale so that you know whether your data can fit on one machine or whether you need to scale the reads. You might ask:

    • What is the expected read-to-write ratio?
    • How many concurrent requests should we expect?
    • Whats the average expected response time?
    • Whats the limit of the data we allow users to provide?

    Different answers require very different designs, so getting the scale right is key to success.

    Question #2 Design Reddit

    Download An Insiders Guide to Ace System Design ...

    Brett Jordan Unsplash

    “Let’s pretend that you are the lead engineer tasked with building a platform like Reddit from scratch.

    Assume youre given the following requirements:

    • Users can make posts in different forums ,
    • Users can include images in their posts,
    • Users can upvote or downvote posts they like or dislike,
    • Users can leave comments on posts,
    • The system has a news feed of posts sorted by both ranking and recency of posts.

    The question would come with the following constraint:

    • The system must be able to support large volumes of users viewing and posting content simultaneously.

    Design Reddit: Our Approach

    There’s no denying, this is a broad system design question. We will follow a similar approach as we did for the previous question.

    First, we will define the problem space. This, again, means clarifying the requirements. In this sample question, the interviewer gave you a concrete list of necessary features. Still, you should first dig deeper into the requirements for additional clarification and detail. For instance, you can ask questions like:

    • Does our system need to support users on mobile and the web, or just one or the other?
    • Will the images be uploaded to the system itself, or will they be links to another hosting service?
    • Are there any necessary performance-related features that would influence our system design?

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    The Architecture Of Large

    You would have to learn about topics like:

    N-Tier applications

    Processing happens at various levels in a distributed system. Some processes are on the client, some on the server, and others on another server – all within one application. These processing layers are called tiers, and understanding how those tiers interact with each other and the specific processes they are responsible for is part of system design for the web.

    HTTP and REST

    HTTP is the sole API on which the entire Internet runs it is the system through which we send every email, stream every Netflix movie, and browse every Amazon listing. REST is a set of design principles to directly interact with the API that is HTTP, allowing efficient, scalable systems with components isolated from each others assumptions. Using these principles and open API makes it easier for others to build on your work or extend your capabilities with extensions to their own apps and services.

    DNS and Load Balancing

    If you have 99 simultaneous users, load-balancing through DNS routing can ensure that servers A, B, and C each handle 33 clients, rather than server A being overloaded with 99 and servers B and C sitting idle. Routing client requests to the right server, the right tier where processing happens, helps ensure system stability. You need to know how to do this.


    Stream Processing

    The System Design Toolbox

    Todd Quackenbush Unsplash

    There are numerous components, algorithms, and architectures that you can use to best design your proposed systems. All components, algorithms, and architectures might be incredibly effective at actualizing one of the previously mentioned dimensions of system design. However, they may do so at the expense of others. Youll need to learn how to juggle and decide between the different elements in your system design toolbox. Unfortunately, each will come with its own unique set of trade-offs and strengths.

    In the end, this is precisely why system design interviews are so interesting for hiring managers. When they ask you to design some system according to a particular set of parameters, they are studying the design choices you make and why. This means that, while you are answering your interview questions, you should always fully explain your thought process and approach. Carefully illustrate why the design choices you made are best given the requirements of the system.

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    What I Learned Through Hundreds Of System Design Interviews

    The experience of working on web-scale systems at Facebook and Microsoft taught me two key skills to approaching the System Design Interview:

  • How to learn the fundamentals of distributed systems quickly and apply these principles in solving real-world problems
  • How to evaluate candidates while interviewing for System Design
  • Heres the counterintuitive part: in the System Design Interview, companies are not actually trying to test your experience with System Design.

    Successful candidates rarely have much experience working on large-scale systems, and interviewers know this. Again, this is a discipline that has only been around for about fifteen years, and like everything else in software engineering, it is evolving rapidly.

    The key is to prepare for the SDI with the intent to apply that knowledge.

    Common System Design Interview Questions

    Ace the System Design Interviews

    An interview for a system designer position is an opportunity to discuss your experience and abilities and to showcase your skills at creating complex systems. You can prepare for your job interview by studying basic design principles and preparing answers to possible questions about them. In this article, we review common questions and answers for a system design interview to help you prepare.

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    Preparing For The Systems Design And Coding Interview

    At Big Tech and high-growth startups, coding and systems design interviews are common – and fairly standard. A lot of people have asked me for preparation advice for these. Here is what I used when getting ready for an E5/E6 Facebook interview, and the one at Uber – where I was hired as a senior software engineer . It’s the same resources I recommend to people who are preparing for Big Tech or high-growth tech company interviews.

    Question #1 Design Youtube

    Szabo Viktor Unsplash

    “How would you design a large-scale, geo-distributed video-sharing platform such as YouTube?”

    Note that such a question is not expecting a truly complete answer. Youtube today is obviously an incredibly complex system. Keep it simple. These system design questions are ultimately looking to see if you can:

  • Pull together a small set of requirements from an ambiguous question.
  • Define a minimum viable product according to these basic requirements.
  • Produce a high-level architecture with all the numerous components that are necessary to implement your design.
  • Discuss the tradeoffs between components and algorithms, and explain your choices.
  • Provide an additional level of detail on any given component or design decision depending on where your interviewer wants to deep-dive.
  • Design YouTube: Our Approach

    First, clarify the requirements with your interviewer . From there, you need to decide which of these are most important and should take priority in your design.

    Next, outline your problem space to some well-established or familiar architectures that are appropriate for the requirements. For instance, many system design questions can be outlined using a client-server pattern. This means that the design includes a user-facing client, middle-tier services alongside a database. iOS apps, on the other hand, would be better served with an MVC pattern .

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    An Excellent And Entertaining Technical Book

    • 4.5 out of 5 stars 78
    • Story4.5 out of 5 stars 76

    This friendly guide teaches you how to apply common algorithms to the practical problems you face every day as a programmer. You’ll start with sorting and searching and, as you build up your skills in thinking algorithmically, you’ll tackle more complex concerns such as data compression and artificial intelligence. This accesible introduction is suitable for self-taught programmers, engineers, or anyone who wants to brush up on algorithms. Each carefully presented example includes helpful diagrams and fully annotated code samples in Python.

  • 1 out of 5 stars
  • S To Approach A System Design Interview

    3 Ways to Ace Your System Design Interview

    As you are studying, heres a 7-step framework that I recommend to approach each problem. For keeping the examples real, we will pick up a common interview question: Design a scalable service like Twitter and see how each step can be applied to designing Twitter.

    Step 1: Requirement Gathering:

    Many candidates think that system design interviews are all about scale, forgetting to put required emphasis on the system part of the interview.

    You need to have a working system before you can scale it.

    As the first step in your interview, you should ask questions to find the exact scope of the problem. Design questions are mostly open-ended, and they dont have ONE correct answer. Thats why clarifying ambiguities early in the interview becomes critical. Candidates who spend time in clearly defining the end goals of the system, always have a better chance of success.

    Here are some questions for designing Twitter that should be answered before moving on to next steps:

  • Who can post a tweet?
  • Who can read the tweet?
  • Will a tweet contain photos or videos
  • Can a user follow another user? .
  • Can a user like a tweet? .
  • What gets included in the user feed .
  • Is feed a list of tweets in chronological order? .
  • Can a user search for tweets .
  • Are we designing the client/server interaction or backend architecture or both .
  • How many total users are there .
  • How many daily active users are there
  • Step 2: System interface definition

    postTweet generateTimeline recordUserTweetLike

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    Gear Up For Your Next Systems Design Interview

    If youâre getting ready for an upcoming technical interview, register for our free webinar to get insightful guidance from industry experts on how to nail technical interviews at top tech companies.

    Weâve trained over 9,000 engineers to land multiple offers at the biggest tech companies and know exactly what it takes to nail tough technical interviews.

    Section : Load Balancing

    If you think about the two words, load and balance, you will start to get an intuition as to what this does in the world of computing. When a server simultaneously receives a lot of requests, it can slow down . After a point it may even fail .

    You can give the server more muscle power or you can add more servers . But now you got to work out how the income requests get distributed to the various servers – which requests get routed to which servers and how to ensure they don’t get overloaded too? In other words, how do you balance and allocate the request load?

    Enter load balancers. Since this article is an introduction to principles and concepts, they are, of necessity, very simplified explanations. A load balancer’s job is to sit between the client and server and work out how to distribute incoming request loads across multiple servers, so that the end user experience is consistently fast, smooth and reliable.

    So load balancers are like traffic managers who direct traffic. And they do this to maintain availability and throughput.

    When understanding where a load balancer is inserted in the system’s architecture, you can see that load balancers can be thought of as reverse proxies. But a load balancer can be inserted in other places too – between other exchanges – for example, between your server and your database.

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    Helpful Things To Remember

  • In the end, there are no set answers in system design interviews. The hiring manager is not waiting for one specific correct answer to their questions. They are concerned with your thought and design process, so be sure you flesh out why you are making your design decisions along with their tradeoffs.
  • You will need diverse knowledge and comfort with many different technologies and systems to answer these questions most effectively. Engineers, for example, will need to elaborate deeply on the systems within their areas of expertise. However, management roles, such as TPM, need to have a much broader range of knowledge over the systems and technologies they use.
  • Network Protocols And Proxies

    Ace System Design Interview – Demo Class

    Network protocols and proxies are among the most fundamental building blocks of system design. And if youre preparing for a system design interview , then understanding these topics is a good place to start.

    Network protocols make it possible for any networked computers to talk to each other, no matter where they are or what hardware or software theyre running. They do this by establishing standard forms for sending and receiving data over the networks physical infrastructure.

    And a proxy is a server that sits between a client and application server to provide some intermediary service to the communication. There are two kinds of proxies that provide different services: forward proxies and reverse proxies. Check out our network protocols and proxies guide to learn more.

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    How Many Design Rounds Do Tech Interviews Have

    Before understanding what the ultimate system design interview checklist covers, letâs look at the nature of design rounds in technical interviews. Design interviews mostly take place during the final stage of the technical interview process, i.e., the on-site interview. Depending on the seniority of the position you’re applying for, the on-site interview may include 1-2 design rounds.

    Note that domain interviews also consist of design rounds. For example, if youâre applying for a Machine Learning Engineer position, there will be 1-2 design rounds.

    My Personal Background In System Design

    In April 2008, I joined an internal team at Microsoft working on a large-scale project building a distributed storage solution.

    Amazon had launched their Simple Storage Service in 2006, and Google launched their PaaS solution Google App Engine the same month I joined the team, so we were in the early land grab of cloud computing. Less than two years later, that project was launched to the world as a new product category: Microsoft Azure.

    When I joined the Azure team, I came from working on Exchange. I understood server storage and client management, but not at this scale, and certainly not distributed across the world. It required a lot of learning on the job.

    Today, the lessons myself and other cloud engineers learned in those early days are codified into the System Design discipline. Now for many companies, the System Design Interview is instrumental in the developer interview process which means it is vital for landing a job and setting your career on a good trajectory.

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    Practice Problems For System Design Interview

    System Design interview questions are broad, open-ended, and have multiple correct answers. Some examples of questions asked during the system design Interview are:

  • Design a tiny URL system
  • Design Facebook messenger
  • Design an autocomplete system, where suggestions will pop up while typing a search query.
  • Design a payment gateway system
  • For more system design interview questions, read:

    What The Udemy Low Level System Design Course Teaches

    3 Ways to Ace Your System Design Interview

    Getting ready for System Design interviews Learn different ways to approach a problem and underline key points Discussing the trade-offs with the interviewer and playing to your strengths Optimizing code using better data structures, according to the scenario Insights into problem extensibility, and begin coding with this as the end goal in mind. Learn to weed out unnecessary information from the problem definition, identify traction, and create a class diagram with it Learn to write test cases for the problem as and when required Necessary exposure and modifications to the API for code sustainability Using encapsulation when required and generate desired accessors and mutators Learn code completion in due interview time. Gain insight into fallback plans in emergency cases

    Ace the Low Level Design interview by solving problems asked in the System Design round of programming interviews

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