Thursday, September 29, 2022

System Design Interview Questions Java

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What Is Cap Theorem

System Design Interview: Architecture of Amazon, Flipkart like e-commerce system with @Gaurav Sen

CAP theorem says that a distributed system cannot guarantee C, A and P simultaneously. It can at max provide any 2 of the 3 guarantees. Let us understand this with the help of a distributed database system.

  • Consistency: This states that the data has to remain consistent after the execution of an operation in the database. For example, post database updation, all queries should retrieve the same result.
  • Availability: The databases cannot have downtime and should be available and responsive always.
  • Partition Tolerance: The database system should be functioning despite the communication becoming unstable.

The following image represents what databases guarantee what aspects of the CAP Theorem simultaneously. We see that RDBMS databases guarantee consistency and Availability simultaneously. Redis, MongoDB, Hbase databases guarantee Consistency and Partition Tolerance. Cassandra, CouchDB guarantees Availability and Partition Tolerance. Complete Video Tutorial.

What Is System Design

The process of establishing system aspects such as modules, architecture, components and their interfaces, and data for a system based on specified requirements is known as system design. It is the process of identifying, creating, and designing systems that meet a companys or organizations specific objectives and expectations. Systems design is more about systems analysis, architectural patterns, APIs, design patterns, and glueing it all together than it is about coding. Because your application will be able to handle the architectural load, designing your system adequately for the requirements of your application will eliminate unnecessary costs and maintenance efforts, as well as provide a better experience for your end-users.

Its impossible to overlook system design when it comes to tech interviews! In the interview, almost every IT giant, whether its Facebook, Amazon, Google, or another, asks a series of questions based on System Design concepts like scalability, load balancing, caching, and so on. So without any further adieu, let us go through the most frequently asked interview questions on System Design.

What Are The Advantages Of Composite Design Pattern In Java

Composite design pattern allows clients to operate collectively on objects that may or may not represent a hierarchy of objects.

Advantage of composite design patterns is as follows.

  • It describes the class hierarchy that contains primitive and complex objects.
  • It makes it easy to add new kinds of the component.
  • It facilitates with the flexibility of structure with a manageable class or interface.

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How Do You Design A Recommendation System

Recommendation systems are used for helping users identify what they want efficiently by assisting them by offering various choices and alternatives based on their history or interests.

  • What are some of the Required Features?
  • Discuss what kind of recommendation system is required – whether it is for movies, e-commerce websites, songs etc.
  • What are some of the common problems encountered?
  • Figure out how to recommend fresh and relevant content in real-time.
  • Possible tips for consideration:
  • Discuss how to use the Eval component for understanding the working of the system.
  • Discuss how to train a collaborative filtering approach.
  • How Do You Design An Application Like Airbnb

    21 System Design and Object

    It allows some users to upload rooms for rent and other users to rent them. Some of the features are only available to admins, publishers, and subscribers.

    21. How do you design an Elevator of the Lift system?We All know about Elevators and Lift as most of us use it. You might have seen them in pairs and in some big office buildings you can see 3 to 4 lifts. You need to design software for that so that it can reach use quickly on different levels. You can assume you have two lifts and a 10-floor building.

    Here is a nice Youtube video which explains the solution to this popular system design interview question, you can watch it right here.

    22. How would you go about designing an e-commerce website like Amazon or Flipkart at scale?

    23. How would you go about designing the e-commerce website using microservices, how will you handle transactions?

    24. How would you design a Parking Lot system? This is an interesting problem and asked for companies like Amazon, Google, Apple, and other FAANG companies.

    You should cover the following use cases

  • Give a user ticket when he enters
  • Generate price when the user exits.
  • Here is a nice YouTube video that explains this problem and the solution. They also discuss APIs, Database models, and database choice. they also discuss on how to make it distributed. We also discuss concurrency. You can also checkout this System Design Interview Course by Exponentto learn how to solve these kind of System design question during interview.

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    Name Different Types Of Operating Systems Also Mention One Disadvantage Of Each Type

    Ans. There are five types of Operating Systems, which are as follows:

    • Real-Time Operating System

    This kind of OS is used while dealing with real-time data. As soon as the data arrives, the execution of the process should be done without any delay. Its main disadvantage is the complexity of the algorithms used.

    • Embedded Operating System

    Embedded operating systems are used to perform certain tasks for a specific device . For example, the embedded OS is used for the functioning of the lift system. The disadvantage of the embedded operating system is that only one task can be performed.

    • Time-Sharing Operating System

    It is also called a Multitasking Operating System. Multiple processes are performed at the same time. Its disadvantage is that prioritized tasks are not performed first. All tasks are given equal priority.

    • Batch Operating System

    Similar tasks are grouped into batches, and the batches are executed one by one. The disadvantage of this type of Operating System is the manual intervention required between two batches.

    • Distributed Operating System

    As the name suggests, the distributed operating system has different systems having their individual

    CPU, memory, and other resources. Its main disadvantage is that extra effort is required for the security of data due to shared data.

    Also Read:

    Explain Some Different Type Of Proxies

    There are many cases where the proxy pattern is beneficial. Let’s have a look at some different proxies.

    Protection proxy

    It controls access to the real subject based on some condition.

    Virtual proxies

    Virtual proxies are used to instantiate the expensive object. The proxy manages the lifetime of the real subject in the implementation.

    It decides the need for the instance creation and when to reuse it. Virtual proxies optimize performance.

    Caching proxies

    Caching proxies are used to cache expensive calls to the real subject. There are many caching strategies that the proxy can use.

    Some of them are read-through, write-through, cache-aside, and time-based. The caching proxies are used for enhancing performance.

    Remote proxies

    Remote proxies are used in distributed object communication. The remote proxy causes execution on the remote object by invoking a local object method.

    Smart proxies

    Smart proxies are used to implement log calls and reference counting to the object.

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    How Do You Avoid A Database Deadlock

    A database deadlock occurs because too many resources have tried to access its locks, and an ideal candidate should know how to avoid typical usage issues such as this one. Your response should show your expertise in using Java architecture. You can list the three main ways in which this situation can be avoided.

    Example: To avoid the database from going into a cyclic wait stage, I would make a queue to verify each request before sending it to the database. Another way to avoid this issue is to use fewer cursors to avoid locking the tables. Using a small transaction is another technique to avoid a database deadlock.

    Preparing For The Systems Design And Coding Interview

    Elevator System Design Using Java

    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.

    Note that none of the below links are affiliate links or sponsored. See my ethics statement on the lack of such links.

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    Grokking The System Design Interview

    This is one of my favorite courses when it comes to learning Software Design or System design. Itâs created to prepare you for the System design interview, but you can also use it to learn how to approach System design in general.

    The Grokking the System Design Interview, is one of the first courses that describes the Large Scale Distributed System Design problems in detail. Even if youâve worked on Distributed Systems before, there are a lot of things that you can learn from this course.

    The authors have created this course to provide you with design choices so that you can understand the requirement, compare approaches, and come up with the best solution for the problem at hand.

    They are also mindful not to provide a solution at a granularity thatâs appropriate for a 45-minute discussion. This makes the course very interesting

    Here is the link to join this course â Grokking the System Design Interview

    Even if you are not preparing for Coding interviews, I suggest you take this course to improve your System design skills. They also have a sequel now called Grokking the Advanced System Design, which enhance this great course even more.

    Best System Design And Object Oriented Interview Resources

    If you need more resources like books, and online courses to prepare for the System design Interview here are my recommendations:

    Thanks for reading this article so far. If you like these Object-Oriented Design Questions, then please share it with your friends and colleagues. If you have any questions or doubt then, please drop a note,P. S. If you need more questions, I suggest you check out the Grokking the Object-Oriented Design Interview course on Educative, an interactive learning platform. This course is a complete guide to master the OODI. It is designed by the hiring managers of Google, Facebook, Microsoft, and Amazon and contains solutions to some of the frequently asked object-oriented design questions from these tech giants.

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    Java Programming: Principles Of Software Design

    This is an excellent course for Java programmer to learn the principles of Software design. In this course, you will learn how to solve real-world problems with Java using multiple classes.

    You will also create programming solutions that scale using Java interfaces. Recognize that software engineering is more than writing code â it also involves logical thinking and design.

    As part of the course, you will also enter a program that analyzes and sorts of earthquake data and developed a predictive text generator if you are a Java programmer, then I highly recommend this course for you.

    How Can You Design A Url Shortening Service Like Tinyurl Or Bitly Etc

    Top 20 System and Software Design Interview Questions for Java ...

    The interviewer asks this question to check if you can create a program that can shorten long URLs like TinyURL or bit.ly. These programs take a long URL and generate a new and unique short URL. You can also put shortened URL here and get the original full-length URL.

    Here, you have to show your solid foundation in design. You can also specify things that are not listed in the example response, such as creating a unique ID for each URL, handling redirects and how you delete expired URLs, etc.?

    You should keep the following features in your mind:

    • Your application must return a URL shorter than the original URL.
    • You have to store the original URL for future purposes.
    • The newly generated URL must be able to link to the stored original URL.
    • Shortened URL should allow redirects to the original.
    • It must support custom short URLs.
    • It should also be capable of supporting many requests at once.

    What type of questions the interviewer can discuss while you answer this question:

    • How can you deal with the issues such as if two users input the same custom URL or get more users than expected?
    • How would you regulate your database storage space?

    What technologies would be best to use to develop such applications?

    • Hashing to link original and new URLs.
    • REST API to load high balance traffic and handle front-end client communication.
    • Use multithreading to handle multiple requests simultaneously.
    • Use NoSQL database to store original URLs .

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    What Is Abstract Factory Pattern

    Abstract Factory Pattern states that define an abstract class or interface for creating families of related objects but without specifying their concrete sub-classes. That means Abstract Factory allowed a class to return a factory of classes. That is why the Abstract Factory Pattern is one level higher than the Factory Pattern.

    • Abstract Factory patterns work around superclasses, which creates other classes.
    • The Abstract Factory Pattern comes under Creational Pattern as this pattern provides one of the best ways to create an object.
    • In the Abstract Factory pattern, an interface is liable for creating a factory of related objects without explicitly identifying their classes.
    • Each generated factory can give the objects according to the Factory pattern.

    Explain The Advantage Of Chain Of Responsibilities Pattern And When It Is Used

    • It minimizes the coupling.
    • It provides flexibility while assigning the responsibilities to objects.
    • It permits a set of classes to act as one. The events produced in one class can be sent to other handler classes with the help of composition.

    Usage of Chain of Responsibility Pattern

    It is used in the following cases:

    • When more than one objects are ready to handle a request, and the handler is unknown.
    • In case the collection or a group of objects that can handle the request must be specified dynamically.

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    What Is Factory Pattern

    • It is the most used design pattern in Java.
    • These design patterns belong to the Creational Pattern as this pattern provides one of the best ways to create an object.
    • In the Factory pattern, we don’t expose the creation logic to the client and refer the created object using a standard interface.
    • Factory Pattern allows the sub-classes to choose the type of objects to create.
    • The Factory Pattern is also known as Virtual Constructor.

    Design An Airline Management System

    Amazon System Design Preparation (SIP)

    A good answer from an interviewerâs perspective would address:

    • Itinerary Complexity: How would multi-flight itineraries work? How would multiple passengers on the same itinerary be handled?
    • Alerts: How are customers notified if thereâs a change to the flight status?
    • External Access: How would the system interact with other actors making reservations to the same flights, such as a front-desk operator for an airline?

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    How Would You Create Your Own Instagram

    Instagram is a photo-sharing application that provides some custom filters to enhance your photo quality. Your application should have photo upload functionality, tagging photos for search, and some basic filters. If you could add share or social network that could be great.

    Btw, if you stuck, you can see the free solution provided on the Educative Grokking System design course as well.

    7. How do you design global file sharing and storage apps like Google Drive or Dropbox?These are used to store and share files, photos, and other media. How do you go about designing things like allowing users to upload/view/search/share files or photos? track permissions for file sharing, and allow multiple users to edit the same document?

    If you like YouTube video, here is a nice one which will teach you how to design a Dropbox or Google Drive or any other document hosting solution:

    Adding Servers And Handling Failing Servers

    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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    How To Prepare For System Design Interviews

    As you can see from the complex questions above, there is a lot of ground to cover when it comes to system design interview preparation. So its best to take a systematic approach to make the most of your practice time, and we recommend the three steps below.

    For extra tips and resources, take a look at our system design interview prep guide and our list of 19 system design interview tips from ex-interviewers.

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