Mastering the System Design Interview: Landing Your Dream Job
In large-scale tech companies and bigger startups, system design questions are essential in tech interviews. Every year, large-scale companies like Facebook, Amazon, Google, Apple, etc., get more than 1 million applications for software development and other engineering roles. They are required to shortlist some of the best candidates. So, their interviews are also challenging. Even many professional engineers can’t succeed in that.
Tech interview loops generally contain 4 to 6 rounds. One or two tech rounds are specially dedicated to the system design interview, and a couple of rounds are specially dedicated to the coding interview.
In this guide, I’ll give you tips and strategies on how you can pass the system design interview at a large-scale startup. Also, I’ve discussed various career trends and roles in system design.
Understanding the System Design Interview
Before we move ahead, let’s understand what the system design interview is and why it is crucial. You will also learn what the hiring manager expects from you in the system design interview.
What is a system design interview?
In the system design interview, you will be given a task to construct a design for a particular application. The given questions can be anything from designing small-scale applications to large-scale social media platforms. An interviewer may ask you to discuss strategies for data modeling and handling large databases.
However, you don’t need to design the system in actuality, but you need to do it hypothetically. So the interviewer can know your approach to building large-scale systems and how you make them scalable, reliable, and easily maintainable.
What are the Parts of the System Design Interview?
The system design interview is an open-ended conversation where the interviewee discusses designing various systems according to the question asked by the hiring manager.
The time duration for the system design interview in most companies is 45 minutes to 1 hour. Below, I’ve explained various steps to answer a system design question and for each step how much time you can spend in an interview.
Step 1: Requirement clarification
As the system design interview is open-ended, there is no correct answer for any question. So, the first step is to ask the interviewer for requirements, and you need to be clear about their expectation from your answer. With clarified requirements, you can design better systems and impress your hiring manager.
You may ask below questions to the hiring manager below to clear the requirements for designing the social media platform.
- Who are the users of the system?
- How many requests does the system need to handle per second?
- What kind of data is required to be stored in the database?
- Clear the read-write ratio of the system to make it consistent.
- Will we need to add a push notification for any feature?
- Will we be required to add search functionality?
- Will users be able to follow other people?
- Will users be able to publish images and videos?
However, questions can differ according to what system you have given to design. In the first 4 to 5 minutes, you can clarify the requirements.
Step 2: Back-of-the-envelop estimation
In the next 5 minutes, you should discuss the estimation of the system scale with your interviewer. It will help you to focus on system scaling, load balancing, caching, etc.
You should consider and discuss the below factors with the hiring manager.
- What read-write ratio, number of concurrent users, and the number of monthly and daily active users are expected from the system?
- Also, discuss how much storage capacity will be needed from the system.
- Also, discuss the required bandwidth and any data limitations.
Once you know the scale of the system, you can start thinking about how you would proceed with designing the expected system.
Step 3: Create the Interface design of the system
When you start designing any system, you should start by designing the components. If possible, you may try to draw a diagram of the interface of the system on the whiteboard during the interview.
Also, you can define the whole architecture of the system and discuss how you would connect each component of the system. This part also includes designing the API to get data from a third-party server or database.
Creating the interface design can take up to 7-8 minutes.
Step 4: Design Database
The next crucial aspect of the system design is the database design and data modeling, which means how you will store the data in the database. Designing the data models will help you to decide the flow of the data between system components in the latter part of the interview.
For the social media application, you can create data models as shown below.
User: ID, Name, Email, PhoneNo, JoiningDate, subscribed
Post: PostID, publishedDate, textContent, imageID
UserFollow: ID1, ID2, ID3
SavedPosts: PostID1, PostID2
You need to decide what kind of database you want to choose from, SQL or NoSQL databases, according to the data you are required to store.
The database modeling can take up to 7-8 minutes as you need to design multiple models and build relations between them.
Step 5: High-level design
In this step, you are required to design the core components of the system. You may draw the components required to develop the system and connect them.
For example, you can discuss the factors below.
- How would you use the multiple servers to handle the multiple concurrent users?
- How would you connect the multiple servers with the database to get data?
- How would you do load balancing with multiple servers?
- How would you replicate the data to handle failures?
Preparing the high-level design for the system can take up to 10 minutes.
Step 6: Scale the design
After completing the basic design of the system, you need to make the system scalable. You can also discuss the horizontal and vertical scalability of the database. Furthermore, you can also take feedback from the hiring manager and improve the basic design of the system accordingly.
To scale the system’s design, you should keep the below factors in mind.
- Discuss how you would partition the data across multiple databases, as you need to store millions of user’s data.
- Discuss how you will be horizontal scaling when users for the system will increase.
- What components of the system require load balancing?
- What data will you cache to make the application faster?
This part can take up to 5 to 7 minutes.
Step 7: Discuss bottlenecks and limitations
In the last 5 to 10 minutes, you need to find the potential issues and limitations of your system, and you should discuss how you can overcome them.
You can discuss the factors below.
- Discuss failure handling and migrating data in such situations.
- Discuss adding enough replicas to serve the data when multiple server fails.
- Discuss monitoring the system when any issue occurs in the system.
The importance of system design interviews
Many freshers and professionals have a question in their mind: Why do companies take system design interviews? Is a coding interview not enough to evaluate the skills of the candidate?
In the system design interview, the hiring manager evaluates your skills in breaking down complex problems into manageable tasks and handling them. When you join a large-scale tech startup, you need to be an all-rounder, and you should know how large-scale system works.
For example, You are giving an interview at Uber, a ride-sharing company. An interviewer might ask you to design the backend system that handles ride requests, driver allocation, and tracking the taxi. In this scenario, you'll required to consider scalability, fault tolerance, and efficient algorithms to match riders with the nearest drivers in real time.
Furthermore, you also get selected, and you need to work on the same stuff. So, it is important to evaluate the candidate’s system design ability.
Is System Design Interview Really Hard?
Nowadays, the system design interview is part of the hiring process for most large-scale tech companies. Sometimes, candidates can crack coding interviews, but they can’t crack system design interviews.
A system design interview is not hard, really, but it's challenging. If you are not well prepared with the fundamental concepts of the system design and haven’t practiced the questions, you can’t crack it.
Also, the overall difficulty of the system design interview depends on the company, the job role you are applying for, and the interviewer. For example, if you are applying for a software developer role in the FAANG (Facebook, Amazon, Apple, Google, Netflix), a system design interview could be more complex than other tech companies.
The complexity of the system design interview depends on the factors below.
- Your Experience: If you have good experience with system design, you can easily crack the system design interview. However, your interview will be complex according to your previous experience.
- Job Role: If you are applying to Amazon for the SDE3 role, your system design interview will be more complex than the SDE1 role.
- Interviewer’s Expectation: Some interviewers expect you to design a high-level architecture system, and some focus on basic system designs and fundamental concepts of the system design. So, the interviewer’s satisfaction is most important.
- Lack of Architecture Skills: If you don’t know the fundamental concepts of computer science, like data structure and algorithm, object-oriented programming, database management, etc., it could be hard for you to crack the system design interview.
In the next section, I’ve explained how you can prepare for the system design interview.
How do I prepare for a system design interview?
To overcome the system design interviews, you must focus on two crucial aspects:
- Learn the fundamental system design concepts like scalability, load balancing, CDN, caching, DNS, Sharding, data modeling, etc.
- Practice the common system design questions asked in past interviews.
Here, I’ve given the step-by-step guide to prepare for the system design interview.
1. Basics of the system design, which should be in focus
System design is a fundamental concept for preparing a design of the distributed system in computer science. Here are some basic concepts of the system design that you should focus on more.
- CDN: A CDN stands for the content delivery network. It is used to store and serve the images, videos, and other resources of the application. It makes applications faster, more efficient, and more reliable.
- Caching: Caching is a high-speed storage located between the database and the application. It stores the frequently accessed data to improve the performance of the application.
- Data partitioning: In data partitioning, data is divided into subparts and distributed across multiple systems to handle the large data.
You can learn more fundamental concepts of system design in 18 System Design Concepts Every Engineer Must Know Before the Interview.
2. Assessing your current knowledge and skills
In the first step, you must start by evaluating your existing knowledge about system design. You should know what system design skills you already have and what you should work on.
You may also evaluate your skills related to software development fundamentals, algorithms, and software architecture.
Furthermore, it would help if you also decided what job role you prefer according to your interests. In the next section, you need to find resources and prepare according to that.
3. Gathering necessary resources
After evaluating your knowledge, you should start gathering resources for your system design interview preparation.
You can collect books, online courses, free YouTube courses, etc., for the preparation.
You can check out the System Desing Interview RoadMap course by DesignGuru to learn the fundamentals of system design.
4. Setting realistic goals and timelines
The next step is to define the realistic goals and timelines for your system design interview preparation.
For example, you can prepare a list of various concepts of the system design and determine how much time you will allocate to each concept and how many days it will take you to be fully prepared with all system design concepts.
5. Educational background and qualifications
Most companies prefer at least a bachelor's degree in computer science-related fields for the system designer role. However, some companies don’t give preference to the education qualification. If you can crack their interview, they can hire you. It could also be the best opportunity for anyone who wants to change their career into the system design field and who hasn’t pursued computer science-related degrees.
If you are preparing for any specific company, you should check their qualification requirements to attend their interview process.
6. Gaining relevant experience and internships
Practical experience is always better than theoretical experience. So, if you can find the 60 to 180 days internship as a system designer, it would be a good kickstart for your career.
The industry experience makes your resume more impressive than training course certificates.
7. Certifications and training programs
If you can’t find the internship, it’s not the last option. You can also enroll in the self-paced training course, and you can get the certificate once you complete the course. You can also include these certificates in your resume to make it more impressive.
You can explore the Grokking SystemDesign Fundamentals course by DesignGuru.
8. Building a strong portfolio
The final step is to make a strong portfolio and resume for your next interview. In your resume, you can add your industry experience if you have any internship experience. Otherwise, you can add the certification that you got after completing online courses.
Also, you can include system design-related skills. In your portfolio, you can explain your experience in detail, and keep in mind that a single-page hosted portfolio makes your profile impressive and separates you from other candidates.
9. System Design Interview Common Questions
Here, I’ve covered some common system design interview questions and given a short guide about each question that you can discuss with the interviewer.
- Design social media platform: To design the social media platform, you are first required to clear the functional and non-functional requirements. After that, you can discuss how you will handle multiple users, how you will secure user’s data, and how you will handle the failures.
- Design the URL shortener: The URL shortener takes the long URL as input and returns the shortened URL, making the URL more readable. In such questions, you can discuss data modeling to store the long and shortened URLs in the database and redirect the short URLs to the respected long URL.
Sometimes, the hiring manager can also ask questions about the basic concepts of the system design rather than asking you to design the system. For example,
- Explain Sharding: Sharding is a concept in which a database is partitioned into multiple databases to handle the server request efficiently. For example, you can divide the 1 TB data into small chunks of the 64GB data.
You can enroll in the Grokking the System Design Interview course provided by DesignGuru to learn more about the system design interview questions.
More about the System Designer Role
As architecture develops the map or design for the building before the construction of the building, the system designer develops the design for the softwares before developing the software.
Below, I have covered what system designers do, the contribution and importance of system designers in product development, and the skills required to become a system designer.
The growing importance of system design in the tech industry
The demand for system designers is increasing as the tech industry is growing and needs to use more scalable and maintainable hardware and technologies to build the application. It will increase more in the future.
Here, I’ve given some facts about why the importance of system designers is increasing in the market.
- Scalability Challenges: With the increasing demand for cloud-based large-scale applications, it is essential to build scalable applications. Making a scalable application is a bit challenging.
- Data Complexity: In the last 2 decades, more technological advancements have occurred, and more and more people have started using modern technologies. So, data modeling is becoming challenging to handle the millions of user’s data.
- User Expectations: Users now expect fast, reliable, and responsive software, making system design critical for meeting these expectations.
- Security Concerns: Security breaches are a constant threat. System designers must incorporate security measures into their designs to protect against cyberattacks.
Key Skills and Qualities Required to Become a System Designer
Here are the skills that are required to become a successful system designer.
- Communication skills are most important, as system designers are required to communicate with clients to know requirements and product developers to explain application requirements.
- Strong analytical and critical thinking skills to solve complex problems.
- The team leadership experience.
- System designers should be able to adapt to new market trends and technologies.
- Technical proficiency in understanding software development and hardware systems.
- Knowledge of the production pipeline.
- Ability to find and solve issues in the system.
- Listening skills are also important to understand the problem better.
Landing Your First System Design Job
Everyday demand for the system designer is increasing. So, if you are a fresher graduate or transitioning your career from other fields to the system design field, read this section thoroughly.
1. Crafting a standout resume and cover letter
The first step is you need to prepare a resume and cover letter to apply for the open jobs. Here are some tips to build a powerful resume.
- Include a system design related project that you have done. If you haven’t, you should take the time and do that first.
- Add internship or any industry-related experience if you have one or multiple.
- You may include your qualifications.
- Add achievements like training certificates.
- Add your soft skills, which also help to build the perfect resume.
2. Effective job searching and networking strategies
After preparing the resume, you need to search for open positions and apply for a system designer role.
Here, I’ve given some tips for finding system design jobs.
- Use online job portals like Naukri, etc., to find the job
- You can also use LinkedIn as a recruiter to post various jobs.
- Go to the networking events if you find any opportunities and ask people for the referral.
- You can also use the cold emailing technique, in which you can directly send your resume to the company in a nice email. Make sure to write a nice and impressive cold email with a unique subject.
Tips for the Interview Day
Till then, you should be ready with your interview preparation as suggested above. Follow the below tips for the interview day.
1. Preparing your mindset
You should be prepared mentally. Believe in your hard work and abilities to boost your confidence. Also, stay calm during the interview and listen to the interviewer carefully. During the interview, keep a positive attitude to accept any challenges.
2. Dressing appropriately
Generally, you should wear the format attire on the interview day, but you may research the company culture and can wear casual attire also. Make sure that your personality is impressive.
3. Bringing necessary materials
If you are going for the on-site interview, don’t forget to bring the necessary material, like an identity card and a hard copy of your resume, with you.
4. Time management during the interview
Make sure to reach the interview location on time. In the interview, you will get limited time to solve particular questions. So, it is important that you don’t waste time on any particular question if you don’t have the confidence to solve it.
In the end, don’t forget to take tips from the interviewer and ask about next steps.
You learned what system design is and how to prepare for the system design interview. For preparing, you need to find good resources and set realistic goals for the step-by-step preparation. Here are a few additional resources:
- Prepare for the system design interview at Google.
- You can also read The Complete Guide to Ace the System Design Interview.