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Hello guys, if you are preparing for Software engineering job interviews, especially for big tech companies like Amazon, Google, Meta, Apple, and Microsoft and worried about System design questions then you are not alone.
System design is an intimidating topic and requires a lot of study and experience to design a real world system. While it's not a rocket science the knowledge of different system design components and concepts are hard to acquire.
In the past, I have shared best System Design Courses and best Software architecture courses as both are related to each other, as well essential System design topics and tips for interviews and in this article, I am going to share 30 System Design Interview Questions with answers for programmers with zero to 3 years of experience.
System Design interview just like other interviews, require you to be up to the task. This means that you have to adequately prepare so that you can have an easy time when going for that interview.
If you don't want to stare at the roof during the interview then you have to find the questions that are usually asked in System Design interviews and practice them hard so that you can be familiar with them.
You can also take help from these best System Design Interview resources which you can use to prepare better for your tech interviews:
- Mastering the System Design Interview by Frank Kane (Ex Amazon Hiring Manager)
- ByteByteGo System Design Course by Alex Xu
- Grokking the System Design Interview on Educative
- System Design Interview Course by Exponent
- System Design Interview --- An insider's guide by Alex Xu
- CodeKarle's System Design Interview Course on Udemy
Top 31 System Design Interview Questions and Coding Problems for Software Engineers and Developers
The following are the top 20 System Design interview questions you can prepare before your next Interview. These are pretty basic question and as a developer you should already be familiar with them but if not then make sure you practice before going for any system design interview.
- What is System Design?
System Design is a process of defining the elements of a system such as the modules, components, various interfaces and architecture. Interviewer ask System design questions to check technical knowledge of candidate.
It's a great way to know whether candidate really understand how things work and computer and tech fundamentals, not just the buzz words like Scaling, High availability, Durability, Resiliency etc.
2. How do you design a web crawler? (solution]
**Answer: A web crawler service collects information/crawl from the entire internet and fetches millions of web documents. Things to keep in mind while designing a web crawler are:
- The approach is taken to find new web pages
- The approach to prioritize web pages that can change in a dynamic way
- To ensure that the web crawler service is bounded on the same domain
You can try solving the question but if you stuck, I recommend you to checkout Grokking the System Design Interview course on Educative, it provides a step by step solution to not just this question but also other System design question.
Here is a nice system design diagram for web crawler:
3. What are key skills you need to crack the System Design Interviews?
Here are key skills to crack the System design interview:
- Good knowledge of Computer Fundamentals
- Familiar with API Integration
- User interaction
- Familiar with how to deploy and scale systems
In general, System designer should have broad view of different technology and how they work and when to use them to make correct choices while designing system.
4. How do you design YouTube? Solution]
Designing a YouTube is an interesting System design question as everyone is familiar with YouTube but a lot goes to design a video streaming service like YouTube. There are a lot of challenges related to storing data, indexing data, and providing streaming service.
Scalability is another major challenge as it needs to be fast and should be able to support millions of users. You can start designing YouTube on your own but if you stuck or need guidance you can see this free tutorial by Alex Xu from his popular System Design Interview Course on ByteByteGo.
Here is a nice flow diagram to explain video upload process:
5. How do you design a URL Shortner like bit.ly or goo.gl?
This is another popular System design question which is often asked during FAANG interview. This question poses a lot of challenge like where are the short URL and target URL will be stored.
How should you create a unique short URL every time for different target URL and return the same short URL for same target URL.
You can try solving this problem on your own but if you stuck then you can also checkout this step by step solution of URL shortner on DesignGuru, one of my favorite portal for preparing System design interview.
If you like their teaching style, I also recommend you to checkout their System Design Interview Bundle where they share their best System design courses for discount.
6. How can you design autocomplete functionality?
Here are important things for developing autocomplete functionality:
- Typeahead suggestion to be provided.
- Queries per second handled by the system.
- Support personalization with the suggestions.
- Amount of data to be stored.
And, if you need solution, here is a nice YouTube video which explains how to design auto-complete functionality
7. In the system design process, where is problem analysis done?\
Problem analysis is done at the systems analysis phase. while its not very important, something to be aware of and I guess, you won't see this question in real System design interview, and if you do, consider yourself really lucky.
8. What are the Types of Documentation in System Design?\
Answer: There are 4 types of documents which are usually created during system design phase:
- Program documentation
- System documentation
- Operations documentation
- User documentation
9. How do you design a Library Management System?
This is another interesting System design problem which is often asked to Software engineers during campus interviews. If you don't know A Library Management System is a software which handle the primary housekeeping functions of a library like keeping records of books and students who loan books.
Library management systems help libraries keep track of the books and their checkouts, as well as members' subscriptions and profiles. You need to design a library Management system which can handle millions of books and thousands of members. The key task here is ability to search books, add books, delete books as well as loan books.
For detailed requirement and step by step solution you can see the link and here is a nice diagram to illustrate the key activities. This problem is also solved in Grokking the System Design Interview Course on Educative
And, If you have Educative subscription then you can see the full solution, even if you don't the solution of this problem is completely free.
**10. Design a Parking Lot Management System ? solution
We all know what a Car park is? in this problem we will design a system which can manage car park. We will focus on the following set of requirements while designing the parking lot:
- The parking lot should have multiple floors where customers can park their cars.
- The parking lot should have multiple entry and exit points.
- Customers can collect a parking ticket from the entry points and can pay the parking fee at the exit points on their way out.
- Customers can pay the tickets at the automated exit panel or to the parking attendant.
- Customers can pay via both cash and credit cards.
You can see here for full system requirement and step by step solution.
**11. 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.
If you want to learn more about Scalability concepts then I highly recommend you to checkout Frank Kane's System Design Course on Udemy where he shared all these key System design concepts in detail.
12. How do you Design an Amazon clone?
Amazon needs no introduction, it is the most popular e-commerce website which does a lot of thing from managing user data, product data, it also maintains inventory, allows seller to sell, buyers to buy, payment, return and so on.
While you don't need to design a full-fledged Amazon app but the key components. The most important thing you need to show is how do you design for scalability and high avaibility which Amazon has
If you get stuck then you can watch this video to learn how to design a e-commerce application like Amazon
13. How do you design a StackOverFlow clone?
StackOverflow is a popular question answer website, which is visited by millions of programmers and developer. You need to design a similar website, the key thing you need to come up with is how do you allow user to add questions, moderation, answering questions, ranking, as well as dividing questions on topic etc. Again scalability is key.
And, if you are curious about the actual StackOverFlow design, here is a nice diagram from ByteByteGo and Alex Xu, author of pouplar and must read System Design Interview --- An insider's guide book, which explains how StackOverFlow current architecture look like
And, if you got stuck you can also watch this YouTube video to get some idea about low level design of StackOverFlow clone.
14. What do you understand by load balancing? Why is it important in system design?
Answer: Load balancing refers to the concept of distributing incoming traffic efficiently across a group of various backend servers. These servers are called server pools.
Modern-day websites are designed to serve millions of requests from clients and return the responses in a fast and reliable manner. In order to serve these requests, the addition of more servers is required.
In such a scenario, it is essential to distribute request traffic efficiently across each server so that they do not face undue loads. Load balancer acts as a traffic police cop facing the requests and routes them across the available servers in a way that not a single server is overwhelmed which could possibly degrade the application performance.
If you wan to learn load balancing in depth as well as other essential system design concepts like Sharding, Caching, and Networking then I also suggest you to join Master the Coding Interview: System Design + Architecture course by Yihua Chang on ZTM Academy
Btw, you would need a ZTM membership to watch this course which costs around $39 per month but also provides access to many super engaging and useful courses like this one. You can also use coupon code FRIENDS10 to get a 10% discount on this course or any subscription you choose.
15. What is Sharding?
Answer: Sharding is a process of splitting the large logical dataset into multiple databases. It also refers to horizontal partitioning of data as it will be stored on multiple machines.
By doing so, a sharded database becomes capable of handling more requests than a single large machine.
Consider an example --- in the following image, assume that we have around 1TB of data present in the database, when we perform sharding, we divide the large 1TB data into smaller chunks of 256GB into partitions called shards.
And, if you want to learn more about Sharding and its role on System Design, I suggest to checkout ByteByteGo and System Design Interview --- An insider's guide book by Alex Xu.
16. How do you Design ATM?
ATM stands for Automated Teller Machine. It's a simple machine which allows you to deposit money, withdraw money, transfer money to other account, and check your account balance. You need to create the software which can mimic these operations.
The key here is correctness and consistency. For example, no matter what happen, account balance of a user must be correct and consistent and no transaction is lost.
Once a transfer is complete, both sender and receiver account must reflect that, no matter what. While this system looks quite simple but implementing these constraints is not easy, when you will try it you will learn a lot.
And, if you ever stuck you can always watch this YouTube Video to find your way as here low level design of ATM is explained in depth.
17 . How do you Design Game of Chess?
This is another interesting problem as we all are familiar with the game of chess but when it comes to designing the game then many programmer look other way.
Designing Game of chess is not trivial as you will need to design a chess board with 8x8 row which is easy as you can use array for that but then you need to distinguish between a square where a piece is present and an empty square, that's also easy, as you can use a boolean flag to indicate that a square is occupied
But, what about different pieces as they behave differently? for example Rook goes straight, horizontal and vertical but Bishop goes diagonal? You can use Strategy pattern for that, your code should just call the move method of a piece and each piece implement it differently.
Well, that's enough hint, you can now work through the problem and start coding, and if you need solution, you can checkout Grokking the System Design Interview Course on Educative, it provide solution of not just chess but many other common System design problems from past interviews on Amazon, Google, Facebook, and other tech companies.
18. What are the various Consistency patterns available in system design?
- Consistency from the CAP theorem states that every read request should get the most recently written data. When there are multiple data copies available, there arises a problem of synchronizing them so that the clients get fresh data consistently. Following are the consistency patterns available:
- Weak consistency: After a data write, the read request may or may not be able to get the new data. This type of consistency works well in real-time use cases like VoIP, video chat, real-time multiplayer games etc. For example, when we are on a phone call, if we lose network for a few seconds, then we lose information about what was spoken during that time.
- Eventual consistency: Post data write, the reads will eventually see the latest data within milliseconds. Here, the data is replicated asynchronously. These are seen in DNS and email systems. This works well in highly available systems.
- Strong consistency: After a data write, the subsequent reads will see the latest data. Here, the data is replicated synchronously. This is seen in RDBMS and file systems and are suitable in systems requiring transactions of data.
19. How do you design Blackjack Card Game?
This is another interesting game which you can design to practice your System Design skill. While I play cards, I never mastered this game so I cannot explain you in simple words like how it works.
All I remember is that you need to draw cards and then you need to add their count. The trick is whether to draw card or not because once your number is more than 22 you are out of the game but for winning, you need to have highest number less than 22.
If you get stuck then here is a nice video which will teach yo how to design Blackjack game using OOP Design technique
if you get stuck, you can watch this tutorial to code your own Blackjack game using HTML, CSS, and JavaScript.
20. How do you design Airbnb or a Hotel booking application?
This system design problem is being asked by a lot of companies lately like Google, Twitter, Uber, LinkedIn, Visa, etc. You need to design a hotel booking system like Airbnb where you can put your room for rent and also allow user to book your room.
Yes, usually, there are two apps, one for customers and others for providers but you can choose to design whatever you want.
And, if you get stuck, here is a nice video which explains this problem and also solution in a step by step guide and if you like this video and Sandeep's teaching style then you can also check his System design course on Udemy where he has solve many such problems.
21. What are the most important aspects of the System Study?\
Answer: System Study has three most important aspects which are as follows:
- Identifying current issues and establishing new goals.
- Study of an existing system.
- Documenting the existing system.
22. As a system designer, how you can design a universal file sharing and storage apps like Google Drive or Dropbox?
The above mention apps are used to store and share files , photos, and other media. We can design things like allowing users to upload/search/view files or photos. It checks permissions for file sharing and enables multiple users to make changes in the same document.
23. How do you design Drop Box?
Dropbox is nothing but a cloud storage where you can backup your file and photos. You need to design a system which can allow you to upload your file, download your file as well designed for high avaibility.
People can also ask you design Google Drive which is similar system and provide cloud storage.
And, if you get stuck, here is a nice video which explains this problem and also solution in a step by step guide.
24. How do you design a Car Rental System?
You need to design an app which allows you to rent a car. The app can also allow you to put your car on rent. Here is nice video which explains this problem and also shows how you can solve it
and here is a youtube video just in case if you get stuck
25. What feature allows one class to derive features from another class?
Answer: The Inheritance feature allows one class to derive features from another class. But more often than not you should use Composition to reuse code
from another class instead of Inheritance. Composition is flexible than Inheritance and there are many benefits of using Composition like easier to test. You can also see my post 5 Reasons to choose Composition over Inheritance for more details.
26. Which language was the first language to be developed as a purely object-oriented programming language?\
Answer: Smalltalk was the first programming language to be developed as a purely object-oriented programming language. While there are many great programming language which support OOP like Java, C++, JavaScript, Python, and C#, none of them are pure object oriented programming language, if you think wearing a purist shoes.
27. How do you design Movie Ticket System like BookMyShow?
You need to design an app where you can book tickets for any cinema hall in a given city for any movie or show. Here is a nice video which explains and solve this interesting system design problem:
28. How do you design a Trade position aggregator or Portfolio Manager?
You need to design a system which can accept Trade and then shows the position for each symbol, much like a Portfolio Manager. Your system needs to support
multiple symbols and it should be fast enough to calculate position in real time.
In order to test your system, you can input a set of trades, both buy and sell side and then query the system to see the live position. You can first try solving this problem yourself but if you stuck you can see my solution of implementing Trade position aggregator in Java for guidance.
29. What is RAID?
RAID stands for a redundant array of independent disks. RAID is the technology that specializes in data storage that combines various physical disk drive components within one or numerous logical units as data redundancy and performance improvement.
30. How do you design a Vending Machine in Java?
This is a common object oriented analysis and design question which is also asked on System design interview.
You need to design a Vending Machine which can vend a couple of products like Coke, Biscuits, Choclates, and Cake. It can accept coins (Nickle, Dime, Pence, and Cent), and small denomination notes
There are multiple ways to solve this problem but solution using State Design Pattern is the simplest one. You can try yourself but if you stuck you can also see my post How to design Vending Machine in Java for step by step solution of this OOP Design problem.
And, if you like video, you can also watch this Step by Step Vending Machine Design video on Exponent's YouTube Channel. If you don't know Exponent also has a great System Design Interview Course where they have 36 lessons and videos with real interview examples, great for system design interview prep.
They also run mock interviews which can be really helpful for interview. I highly recommend them to checkout.
31. How to design a Car hailing app like Uber, OLA, Lyft, or Grab?
In this problem you need to design a Cab booking System like Uber/ Ola/ Grab/ Lyft, etc. Here is a nice video which explains this problem and also gives tips on how to solve it.
That's all about 31 System Design Interview Questions and Answers for Coding Interviews. You will surely do better in your interview if you have mastered all the questions with answers in this article.
That is the best thing you can do to yourself because this interview is about to change your life in some way. Just be ready for that day and you will see for yourself that everything can be easy and perfect if you do nothing but prepare.
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Thanks for reading this article so far. All the best for your System Design and Coding interviews and if you have any questions which don't know answer or any doubt feel free to ask in comments.
P. S. --- If you struggle to solve System Design Questions then I highly recommend you to go through a comprehensive System Design course like Grokking the System Design Interview course on Educativewhich is great way to prepare for System design interviews.
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