30 System Design Interview Questions (With Example Answers)

By Indeed Editorial Team

Published 2 August 2021

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

Interviewing for a position requiring system design expertise is an opportunity to discuss your experience and highlight your ability to create complex systems. When speaking with a potential employer, how you communicate your knowledge can help you prove that you are a qualified candidate for the job. You can prepare for your job interview by studying basic design principles and planning answers to possible questions about these ideas. In this article, we review common system design interview questions and answers to help you prepare for your next interview.

What are system design interviews?

System design interviews typically test the knowledge and design skills of professionals seeking an upper-level position in a technological field. In system design interviews, applicants answer broad questions by developing a prototype system using key components to outline a model before explaining their approach. Interviewers may also ask job candidates questions to determine their technical knowledge and experience. They are commonly used for roles like development manager, system engineer or technical program manager.

System design interview questions with sample answers

System design interview questions combine foundational knowledge with skill application. Here are the most common types of questions interviewers ask and their sample answers:

1. Can you name some metrics for measuring system performance?

Interviewers may ask you this question to find out if you understand the different ways to measure system performance and the importance of these monitoring techniques. When you answer, explain how these metrics help ensure a fast and efficient system.

Example: "The three most common metrics used to measure a system's performance are availability, latency and throughput. These metrics help system designers measure the speed of a user's experience while interacting with a system. Availability shows us how often a system responds to a user in a ratio of Uptime vs. Downtime. Latency refers to the speed at which a message is delivered in milliseconds. Finally, throughput measures the amount of data that successfully travels through a system to a user in a specified time period. Throughput is typically calculated in bits per second."

2. What is load balancing, and why is it important to system design?

Your interviewer may ask this question to hear you explain one of the fundamental principles of system design. It is important to prove your knowledge of this basic design function by clearly stating how load balancing works and how it contributes to the reliability of a system.

Example: "Load balancing is the essential process of allocating tasks across computing nodes to ensure the functionality of a system. The two main load balancers, L4 and L7, are named for the OSI model of network communication.

Load balancing improves the quality of a design, using either hardware or software to create a more reliable system. A system's load balance impacts system security and user experience. An effective load balance also allows for continuous software updates and scaled server space to accommodate changes in system use."

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3. How would you design a tinyURL system?

A hiring manager might ask this to allow you the opportunity to show your solid foundation in design with a detailed explanation and a specific example. Prove your understanding that a TinyURL is an URL service that creates a shorter, unique URL after users enter a long URL. Consider focusing on other basics not listed in the example response like how you create a unique ID for each URL, how you handle redirects and how you delete expired URLs.

Example: "When I was working for a public instant messaging site, I created a simple system where every message was limited to 140 characters. It also necessitated shortened URLs of about 30 characters. This TinyURL system is also useful when entering hyperlinks in emails or on a smartphone, where there is room for error.

TinyURL is also a perfect example of the hashtag table. This data structure associates keys with values and is a simple connections code. By using this basic 16-bit hash table, I was able to optimise usability and meet the needs of the system."

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4. How would you design a search engine?

Sometimes search engines are needed within a specific department of a company to systematically locate an item or important employee information. Hiring managers want to see that you can tailor designs to the needs of the company. You can detail some of the overall architecture of a search engine using the foundation below.

Example: "Before I relocated here, I created a search engine that performed keyword searches. I began by building an indexer, which is a piece of software that crawls and produces results in a data structure. The crawler would put web page links together and group them or dump them into sets. I had the crawl set for H1 and H2, rather than H3s. I also checked outbound links to avoid spammers. Lastly, I checked the serving results to verify that the design was working at optimal capacity and relevancy."

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5. How do you design a shared drive?

Hiring managers ask this to explore algorithm basics and backgrounds. Before you begin, make sure you understand the purpose of the task. Knowing if changes are be registered in real-time, if locking is necessary and if the drive must be naturally convergent can help you give a complete answer.

Example: "Shared drives work on differential synchronisation which keeps two or more copies of the same document synchronised with each other in real-time. Therefore, if a change is made in one version, the same alteration happens on all the others. It is a complex challenge, but differential synchronisation is scalable and fault-tolerant. The three common approaches are ownership, event passing and three-way merges.

I created a shared drive in my previous position to support in-house document sharing for one of our clients. I used event-passing to allow for real-time collaboration, as the locking or ownership approach would only allow the first one opening the document to make any adjustment. Using this approach, their employees were able to work collaboratively even when out of the office or on different schedules."

6. How would you incorporate microservices into an e-commerce platform?

Microservices combine independent modules together to form a collaborative system instead of using single or monolithic system construction. As businesses continue to use digital services. Your interviewer may ask this question to determine your knowledge of industry trends and web application architecture.

Example: "Microservices effectively customise e-commerce services for a business. In my previous job, I helped customise e-commerce services for a gig hosting business that connected administrative freelance contractors with companies seeking specific one-time services. Using microservices, I was able to create an interconnected platform using API gateways throughout a distributed system. This gave the company the opportunity to make updates quickly and offer personalised dashboards to users."

Related: Microservices Interview Questions (With Sample Answers)

7. How do you design a recommendation system?

Recommendation systems help users find what they want more efficiently. They assist clients and customers by offering alternatives and allowing for more choices. Hiring managers inquire about this to see if you can create systems that are user friendly and focused.

Example: "One of my former clients found that their customers were struggling to find options on their website. Their search had to be exact in order to find the product. I suggested we implement a recommendation system to help with customer satisfaction and possibly sales. Using the most prominent approach of collaborative filtering, I designed the system to weave a sort of information tapestry that provided customers with suggestions based on user similarity. The system became more user friendly and produced a 10% increase in sales for my client."

Additional system design interview questions

Here are some of the additional questions typically used in a system design interview:

  • Can you choose a popular social media platform and explain how you would design it?

  • How would you design a limit book for a trading system?

  • Can you explain the process of creating a global file-sharing or storage system?

  • Can you explain the process for creating a chat or messaging system?

  • What kind of algorithm would you use to create a newsfeed for a social media website?

  • What are the most important components for designing an e-commerce website?

  • What are parking lot systems, and how are they designed?

  • How would you determine the goal and scale of a system?

  • Why are network protocols and proxies considered a fundamental part of system design?

  • How can a database impact the scalability and speed of a system?

  • How would you design a proximity server for restaurant and retail e-commerce?

  • What is a leader election algorithm?

  • Why is it helpful to use queues and pub-subs in a system design?

  • Can you name some techniques used to stream large amounts of data on or off of a server?

  • How would you design a traffic control system?

  • Can you explain how sharding is used to scale a database system?

  • How does caching improve the time it takes a system to retrieve data?

  • Can you explain how you would design a ride-sharing system?

  • How would you design a video sharing system?

  • What design elements would you use to create a global message board and social networking platform?

  • How would you design a global video streaming service?

  • Can you explain your design for an API rate limiter?

  • Can you explain the various networking models?

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