Most Common System Design Interview Questions
Before we get to a complete list of system design interview questions, lets take a minute to go over the five most common questions that we found in our research.
These questions come from Glassdoor interview reports by software engineers, engineering managers, and technical program managers at Amazon, Facebook, Google, and Microsoft.
Together, these five questions made up nearly 30% of the system design interview questions that we collected across these roles.
To help you prepare answers to these questions, weve included a framework that you can use to structure your thinking. For the sake of brevity, we wont be writing out entire sample answers for each question, but well be linking to full answers that you can use to check your work.
Lets get started.
The Google Technical Interview Process
The is theultimate test of your programming and problem-solving abilities. The process is spread across multiple rounds. It begins with the initial phone screen with a recruiter, followed by the technical phone screen, and ultimately, the on-site interview.
While the technical phone screen is conducted remotely, recruiters invite you to the Google campus for the on-site interview. The on-site comprises a coding, design, and behavioral round, each built to test your capabilities as a programmer and how good a fit youâd be for your role.
To learn more about the interview process, check out our comprehensive .
Topics To Prepare For Systems Design Interview
The systems design interview rounds aim at testing how you break down a large problem and tackle different parts of it. So while your tech skills are important, your critical thinking is also at display during these rounds. Narrowing down the topics to prepare for such an interview is not easy.
However, based on our experience of training over 9,000 software engineers, the following are some of the key broad categories that you should consider while preparing for a systems design interview:
- Basics of systems design
- Measuring the performance of scalable systems
- MapReduce and distributed file systems
- Systems design case studies
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Design Dropbox/google Drive/google Photos
Design a file or image hosting service that allows users to upload, store, share, delete and download files or images on their servers and provides synchronization across various devices.
Things to discuss and analyze:
- Approach to upload/view/search/share/download files or photos from any device.
- Service should support automatic synchronization between devices, i.e., after updating a file on one device, it should get synchronized on all devices.
- ACID property should be present in the system.
- Approach to track permission for file sharing.
- Allowing multiple users to edit the same document.
- The system should support storing large files up to a GB.
Top 25 System Design Interview Questions For Programmers
Without any further ado, here is the list of some of the most popular System design or Object-oriented analysis and design questions to crack any programming job interview.
1. How do you design the Vending Machine in Java? You need to write code to implement a Vending machine that has a bunch of products like chocolates, candy, cold-drink, and accept some coins like Nickle, Dime, Quarter, Cent, etc. Make sure you insert a coin, get a product back, and get your chance back. Also, write the Unit test to demonstrate that these common use cases work. If you get stuck you can read my two-part articles about solving these classical system design questions.
2. How do you design a URL Shortening service like goo.gl or bit.ly? This one is another common System design question. You have given a long URL, how would you design a service that would generate a shorter and unique alias for it? If you are not familiar with URL shortener service have a look at some of the popular ones like goo.gl from Google and bit.ly which is used by Twitter.
Make sure to provide database schema and rationale behind some design decisions like how long you keep the data, how to get stats and analytics etc. If you get stuck, you can follow the solution given on Grokking the System Design Interview course on Educative.
If you need a refresher on Data Structure then you can check out Data Structure and Algorithm in Java course and If you feel stuck you can check out my solution here.
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What Is A Systems Design Interview
Systems design interviews is an important part of tech interviews at FAANG and tier-1 tech companies. In these interviews, companies evaluate your ability to create scalable systems with low latency, capable of reaching millions of users.
These interviews typically consist of many open-ended interview questions, where you essentially have to discuss the technicalities behind complex, scalable systems. Knowing and applying concepts related to relational databases, sharding techniques, and network protocols is also crucial to ace this round.
Example Project From My Resume:
Built a timetable management system in Flask. The students and faculty can visualize their timetable, check for clashing courses as well as add their timetable to Google Calendar. Used pytest for unit testing. Travis builds and tests each commit to the GitHub repository. If the tests pass, it pushes the docker image to dockerhub and deploys the application to Heroku. Also setup ELK stack for monitoring and logging.
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Featured Pragmatic Engineer Jobs
The above jobs score at least 10/12 on The Pragmatic Engineer Test. Browse more senior engineer and engineering leadership roles with great engineering cultures, or add your own on The Pragmatic Engineer Job board and apply to join The Pragmatic Engineer Talent Collective.
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Design A Social Media App
One of the most common system design interview questions, design a social media app requires candidates to tackle an incredibly complex taskbuilding a large, intricate system in 60 minutes or less. For this example, well assume the interviewer asked us to design Twitter.
Ask clarifying questions
- Is the interviewer looking for a design of the core features, or a high-level overview of the whole service?
- What are the constraints of the system?
- What are your assumptions?
- Back-of-the-envelope calculations: average KBs per tweet, size of new tweet content per month, read requests and tweets per second, etc.
- High-level components: write, read, and search APIs types of databases SQL vs NoSQL etc
Drill down on your design
- Components that you could dive into: how a user views the home timeline or posts a tweet, the intricacies of the database design, etc.
Bring it all together
- Consider: does the final design address the bottlenecks youve identified? Does it meet the goals you discussed at the beginning of the interview? Do you have any questions for the interviewer?
For a full answer to this question, take a look at the video guide below from Success In Tech or this text guide from donnemartin on GitHub.
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Section : Networks And Protocols
“Protocols” is a fancy word that has a meaning in English totally independent of computer science. It means a system of rules and regulations that govern something. A kind of “official procedure” or “official way something must be done”.
For people to connect to machines and code that communicate with each other, they need a network over which such communication can take place. But the communication also needs some rules, structure, and agreed-upon procedures.
Thus, network protocols are protocols that govern how machines and software communicate over a given network. An example of a network is our beloved world wide web.
You may have heard of the most common network protocols of the internet era – things like HTTP, TCP/IP etc. Let’s break them down into basics.
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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How To Nail Your Next Tech Interview
Google is one of the most valuable companies in the world and offers a broad spectrum of consumer- and business-centric services. Its phenomenal culture makes it one of the best companies to work for software engineers and developers. As part of its technical interview process, Google conducts a systems design round to evaluate the engineering design skills of applicants. This round mostly happens during the on-site interview, along with the coding and behavioral rounds.
To ace Googleâs system design interview requires a good understanding of design fundamentals and the ability to build and work with scalable systems.
This article focuses on acquainting you with and what sort of systems design interview questions to expect.
Hereâs what we will cover in this article:
- What is a system design interview?
- Google system design interview process
- Google system design interview questions
- Tips to prepare for and crack system design interview
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:
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Practice With Mock Interviews
The first step is always to practice by yourself, as we touched on above. Once youve got the framework down, start interviewing yourself out loud as you practice. Play both the role of the interviewer and the candidate, asking and answering questions. This will help you develop your communication skills and your process for breaking down problems.
Preparing For The System Design Interview
- What is a system design interview and what it should test
- A template that can be used on any system design interview question
- Many exercises throughout the course to help you get a hang of system design
- Easy to understand explanations
- Many case studies of real world systems which are mostly asked in the System design interviews
- Ways to tackle situations in different stressed conditions
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Questions Related To This:
- Why did you use Flask not Django?
- Did you use a database? Which database?
- You built this for your college, but if you were to have a million new users overnight from various colleges, how would you scale?
- Is there any single point of failure in your project?
- How would you deploy this in real life? Blue-green, rolling or canary deployment? Why?
As you can see, I was not asked to design any large scale system like Facebook or Instagram but they still tested my system design knowledge. It is not necessary that you know the correct answers to all the questions but it is expected that you should be able to justify your own design decisions.
Any Questions About Google Software Engineer Interviews
If you have any questions about Google coding interviews, do not hesitate to ask them below and we will be more than happy to answer them. All questions are good questions, so go ahead!
Applying for other companies? Check out our other guides for , , Microsoft, , and Airbnb software engineer interviews.
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How To Prepare For The System Design Interview In 2022
For many software engineers, the System Design Interview 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 Is The Google Interview Different From Other Companies
Google isnt shy about sharing their hiring practices. In fact they have a whole page dedicated to exactly that.
The interview process begins with at least one phone screen and, if successful, a series of onsite interviews. The Google phone screen and onsite portions are fairly typical across the board of technical interviewing, but the process at Google is unique in a couple specific details:
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How Are Performance And Scalability Related To Each Other
The ability to handle a large amount of traffic in any application is referred to as scalability, whereas performance is about testing the speed with which the application is running. The increased performance is directly proportional to the number of resources added to the system. The ability to handle larger data sets in the event of growing work makes scalability directly related to the performance of any design. Performance problems might affect just one user, whereas the system might eventually become slow in case of scalability issues due to heavy data load.
The Concepts You Need To Know
To be able to speak intelligently about system design, youll need to acquire a knowledge base of related concepts. Of course, this doesnt mean that you need to know every detail related to sharding, load balancing, queues, etc.
However, you will need to understand the high-level function of typical system components. You’ll also want to know how these components relate to each other, and any relevant industry standards or major tradeoffs.
To help you get the foundational knowledge you need, we’ve put together a series of 9 system design concept guides.
Here’s a the full list:
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My Preparation Strategy For System Design Interviews With Silicon Valley Companies
In software engineering, system design defines the components, modules, interfaces, and data for a system to meet specified requirements. Most companies do not ask system design to freshers. However, when I was interviewing for a Full-Time Software Engineer role, a few companies had system design interview rounds.
In this blog post, I will talk about the various type of system design interviews and how I prepared for them.
Faqs On Google Tech Interviews
Q. Are coding rounds more important than design rounds at the Google interview?
For junior software positions, coding rounds are more important than design rounds. For senior developer and managerial positions, design rounds and behavioral rounds hold more weight in hiring decisions.
Q. What type of behavioral questions are asked at Googleâs technical interview?
Behavioral questions asked at Googleâs interview are typically around the following topics:
- Past projects
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