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How To Answer System Design Interview Questions

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How Do You Prepare For A System Design Interview

How to answer a System Design question?

In a System Design Interview, interviewers ask the candidate to design a web-scale application. For example, they might ask you to , design Netflix, or design Uber backend.

Unlike a coding interview question, System Design Interviews are free-form discussions, and theres no right or wrong answer. Instead, the interviewer is trying to evaluate the candidates ability to hold a conversation about the different aspects of the system and assess the solution based on the requirements that might evolve during the conversation.

The best way to think about the conversation is to imagine that you and a colleague are asked to design a large-scale system, and you are hashing out the details on the whiteboard. You are understanding the requirements, scope, and constraints before proposing a solution.

So how do you design a system in an interview if you have never built one in real life? To crack your system design interview, youll need to prepare in three areas:

  • Distributed system fundamentals
  • The architecture of large-scale web applications
  • Designing distributed systems
  • Each of these dimensions flows into the next.

    If you dont know the fundamentals, you wont be prepared to architect a service if you dont know how to put those systems together, you wont be able to design a specific solution once youve designed large-scale systems, you can take lessons learned and integrate them into your base knowledge.

    Lets look at each of these dimensions in order.

    How Is Horizontal Scaling Different From Vertical Scaling

    • Horizontal scaling refers to the addition of more computing machines to the network that shares the processing and memory workload across a distributed network of devices. In simple words, more instances of servers are added to the existing pool and the traffic load is distributed across these devices in an efficient manner.
    • Vertical scaling refers to the concept of upgrading the resource capacity such as increasing RAM, adding efficient processors etc of a single machine or switching to a new machine with more capacity. The capability of the server can be enhanced without the need for code manipulation.

    This has been demonstrated in the image below:

    Horizontal scaling vs. Vertical scaling:

    Follows ACID properties. Follows BASE properties.

    Check out more differences here.

    Why Is Documentation Control Necessary

    The interviewer most likely will want to evaluate your perception of following standard procedures when documenting changes and integrations to system design. You can use your answer to show the interviewer that you value the importance of documenting each project as well as your experience evaluating which approach to take for documentation.

    Example:”Documentation control is a crucial part of my job because it enables other IT professionals, staff and users to view each component of a module within a system design. I have extensive experience with this aspect of the job, and I worked to keep each documentation updated to reflect all recent progress within a specific system design.”

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    How To Prepare For The System Design Interview In 2022

    For many software engineers, the System DesignIinterview remains a mysterious challenge.

    Most engineers have never actually worked on large-scale systems before, so having to explain how to build one seems daunting. And because system design interview questions can be so open-ended, it is hard to know the right way to prepare.

    Before I spent eight years working on distributed systems at Microsoft and Facebook, I definitely felt this way. But now, as someone who has participated in hundreds of system design interviews, I can assure you that there is a way through.

    In this post, I will discuss:

  • What interviewers are looking for in a System Design Interview

  • How any developer can prepare to confidently answer System Design questions

  • How Can You Design The Websites Or Apps Like Facebook Twitter Or Instagram

    System design interview questions and answers pdf ...

    The interviewers ask this question to see how you can deal with a huge quantity of users because it will require many storage systems and other complications. When we design social media services that have to handle millions or billions of users, we must focus on the following components:

    • Huge and efficient storage and search for posts or tweets.
    • Newsfeed generation and maintenance
    • Social Graph

    Many times, interviewers spend the whole interview discussing the design and your creative idea of the newsfeed.

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    Design A Parking Lot System

    • What are some of the Required Features?
    • The parking lot can have multiple levels where each level has multiple rows for parking spots.
    • The parking lot can support parking for cars, buses, motorcycles hence spots can be of multiple sizes.
    • Consider the parking lot capacity at the time of designing the system.
    • Design appropriate pricing for each parking spot.
  • What are some of the Common Problems encountered?
  • What should happen to the parking lot system if every spot is occupied?
  • Assigning parking lot spots of smaller size to vehicles of a bigger size.
  • Possible tips for consideration:
  • Think of an algorithm for assigning an appropriate parking spot to a vehicle.
  • Think of different entities required for designing the system.
  • What Is Necessary For The Design Of A Waste Management System

    Garbage collection guarantees that a Java system runs properly and relieves the programmer of the need to do it manually. Hiring managers want to know that you understand the ins and outs of numerous systems. A garbage collector optimizes memory usage in computers.


    “One of my latest clients need additional memory, however there was a problem with constantly having to deal with memory deallocation.” The purpose of trash collection is to give the illusion that a system has an infinite quantity of memory. In reality, the system is repurposing memory. When a system is slow to respond, a trash collector enters and collects items that are no longer in use. I configured their system in such a way that any item that is referenced or recursive in nature persists. Following that, it proceeds carefully and marks everything that has not been referenced and sweeps only that. Utilizing the mark and sweep approach in conjunction with the void command enables memory to be repurposed and opened up that is no longer in use. With this in place, my customer benefitted from a quicker system that required less maintenance.”

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    List Of Ui Design Interview Questions: Behavioral

    With behavioral interview questions, employers want to see how you handled past situations. Your response will give employers insight into how you may handle tasks or solve problems in the future. For these types of interview questions, specificity is key. Provide an example of a past situation in your career, describe the actions you took, and share the results or outcome. Candidates will stand out if they can offer examples of real conflicts or challenges that an interviewer might envision developing at their own company, and then provide a level-headed and comprehensive solution.

    A few examples of behavioral UI Designer interview questions are:

    What Would You Use Operations Documentation For

    Amazon System Design Preparation (SIP)

    Because these aspects of system design can become complex, the interviewer might want to gauge your expertise with working on projects that require all forms of documentation. You can use your answer to highlight specific examples of how you’ve used operations documentation in the past.

    Example:”Operations documentation uses all components of the necessary information for processing, distributing and clarifying system outputs. For example, in my last role, I used operations documentation to keep track of input files, sources, output files and destinations that I integrated into my design.”

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    The Manager Of Component ‘a’ Says His Functionality Is More Important Than That Of Component ‘b’ The Manager Of Component ‘b’ Says His Is More Important Than That Of Component ‘a’ You Can Only Implement One A Or B But Not Both

    The key question to ask is definition of “IMPORTANT”. Is it important to the managers , important to the end consumer or important for Amazon. The first one needs to be thrown out immediately and the others must be quantified based on achievability, impact on end user and ROI.Less

    If the rock were neutrally buoyant the water level would remain the same. It is heavier than water which causes it to displace more than its own volume while in the boat compared to at the bottom of the lake. Therefore the water level of the lake would go down.Less

    These answers are troubling. The only correct answer so far is Ben. The water level goes down.Less

    The weight of the boat plus you plus the rock has already displaced the height of the water. The only time the water level will change will be when the rock is mid air.Less

    What Do You Understand By Content Delivery Network

    Content delivery network or in short CDN is a globally distributed proxy server network that serves content from locations close by to the end-users. Usually, in websites, static files like HTML, CSS, JS files, images and videos are served from CDN.

    Using CDN in delivering content helps to improve performance:

    • Since users receive data from centres close to them as shown in the image below, they don’t have to wait for long.
    • Load on the servers is reduced significantly as some of the responsibility is shared by CDNs.

    There are two types of CDNs, they are:

    • Push CDNs: Here, the content is received by the CDNs whenever changes occur on the server. The responsibility lies in us for uploading the content to CDNs. Content gets updated to the CDN only when it is modified or added which in turn maximises storage by minimising the traffic. Generally, sites with lesser traffic or content work well using push CDNs.
    • Pull CDNs: Here new content is grabbed from the server when the first user requests the content from the site. This leads to slower requests for the first time till the content gets stored/cached on the CDN. These CDNs minimizes space utilized on CDN but can lead to redundant traffic when expired files are pulled before they are changed. Websites having heavy traffic work well when used with pull CDNs.

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    List Of Ui Designer Interview Questions From Top Companies

    To give you an idea of the range of UI Designer interview questions you may be asked, here are a few questions from top tech companies.

    • Tell me about a time when your team had difficulty collaborating.
    • How would you design a digital clock that had only two buttons and could only display numerical characters? What other capabilities would you add?
    • Show us an example of a website with great design.
    • How do you measure the success of your designs?
    • Please describe a challenge you met in a previous project.
    • How do you deal with pushback with upper management?
    • Tell me about a time when you had to get a project or initiative completed with limited resources.
    • Tell me about a time when you exceeded the expectations of a goal.
    • How would you handle a situation where you are not able to meet a deadline?
    • Give me an example of a time there was a conflict between you and your team or someone on your team. How were you able to resolve that conflict


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    What Is User Documentation And What Should It Include

    System design interview questions and answers pdf ...

    With this question, the interviewer may want to evaluate your knowledge of various documentation processes, as well as your understanding of what each aspect should cover. Use this question to highlight your experience and skills with creating user documentation as well as using the data to drive your system designs.

    Example:”User documentation is a means of providing instructions and information for users who interact with the system. Appropriate user documentation in my experience should include a system overview, including overviews of system menus, contents, data entry screens and other processing instructions. This should make the user experience smooth and reduce issues with user interaction.”

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    Design An Api Rate Limiter

    Design a service or tool that monitor the number of requests per a window time a service agrees to allow. If the number of request exceeds the rate limiter blocks all the excess calls.

    Things to analyze and discuss:

  • Limiting the number of requests an entity can send to an API within a time window, for example, twenty requests per second.
  • Rate limiting should work for a distributed setup, as the APIs are available through a group of servers.
  • How to handle throttling .My Personal Notesarrow_drop_up
  • Differentiate Between Compile Time Polymorphism And Runtime Polymorphism

    Compile Time Polymorphism

    A. It is also called Static Polymorphism.

    B. This type of polymorphism happens at the compile time.

    C. The compiler gets to decide the shape or value that has to be taken by the entity in the photograph.

    A. It is also called Dynamic Polymorphism.

    B. This type of polymorphism happens at the run time.

    C. Here, the shape or value that has to be taken by the entity in the picture is not decided by the compiler.

    3. Name different types of constructors in C++.Ans. There are three types of constructors in C++, which are as follows:

    • Default Constructors: It does not take any argument and has zero parameters.
    • Parameterized Constructors: These types of constructors take some argument.
    • Copy Constructors: It is a member function, and its basic function is to initialize the object using another object of the same class.

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    How Are Design Patterns Categorised

    As the interview proceeds, interviewers may test your knowledge of different design patterns. Your answer can indicate how thorough you are with the foundation and basics of design patterns. Explain the categories in simple sentences.

    Example:”The three categories of design patterns are creational patterns, structural patterns and behavioural patterns. Creational patterns allow freedom to choose how to create objects while hiding the logic. Structural patterns identify and simplify class and object composition, define relationships between objects and use inheritance to give additional functionality to objects. Behavioural patterns identify how the objects communicate with one another.”

    Adding Servers And Handling Failing Servers

    SDM/TPM Interview Systems Design

    So – what happens if one of the servers that we are sending traffic to dies? The hashing function still thinks there are 5 servers, and the mod operator generates a range from 0-4. But we only have 4 servers now that one has failed, and we are still sending it traffic. Oops.

    Inversely, we could add a sixth server but that would never get any traffic because our mod operator is 5, and it will never yield a number that would include the newly added 6th server. Double oops.

    // Let's add a 6th serverservers =>  // let's change the modulo operand to 6request#1 =>  hashes to 34 =>  34 % 6 = 4 =>  send this request to servers =>  Server Erequest#2 =>  hashes to 23 =>  23 % 6 = 5 =>  send this request to servers =>  Server Frequest#3 =>  hashes to 30 =>  30 % 6 = 0 =>  send this request to  servers =>  Server Arequest#4 =>  hashes to 14 =>  14 % 6 = 2 =>  send this request to servers =>  Server C

    We note that the server number after applying the mod changes .

    In effect, the result is that half the requests are now being routed to new servers altogether, and we lose the benefits of previously cached data on the servers.

    For example, request#4 used to go to Server E, but now goes to Server C. All the cached data relating to request#4 sitting on Server E is of no use since the request is now going to Server C. You can calculate a similar problem for where one of your servers dies, but the mod function keeps sending it requests.

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    Section : System Availability

    Software engineers aim to build systems that are reliable. A reliable system is one that consistently satisfies a user’s needs, whenever that user seeks to have that need satisfied. A key component of that reliability is Availability.

    It’s helpful to think of availability as the resiliency of a system. If a system is robust enough to handle failures in the network, database, servers etc, then it can generally be considered to be a fault-tolerant system – which makes it an available system.

    Of course, a system is a sum of its parts in many senses, and each part needs to be highly available if availability is relevant to the end user experience of the site or app.

    Explain The Benefits Of Design Patterns In Java

    It is quite possible that the interviewer may ask this question. You can explain the general benefits of using design patterns in Java. You can also add some specific benefits you have encountered while using design patterns in your work so far.

    Example:”Design patterns provide a template for developers which they can use in multiple projects. Design patterns in Java help the programmer design flexible and smart code and easily identify unwanted code. It benefits me as I can be faster at my job because of the ability to customise the architecture of multiple systems instead of repeatedly coding everything by hand.”

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    What Are The Essential Skills Of System Designers / What Skills Are Needed To Be A Designer

    The System Designers must have the following qualities:

    • They must be able to understand and solve complex problems.
    • They have a logical and analytical approach to solve problems and customer’s requirements.
    • They must have good communication skills.
    • They must be able to work independently as well as part of a team.
    • They must have a good knowledge of IT and the ability to apply it in their project.
    • A system designer should be capable of directing the work of others.

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