6 System Design Interview Questions With Helpful Answers

Updated May 26, 2023

An interview for a system designer position is an opportunity to discuss your experience and abilities and showcase your skills in creating complex systems and software design. You can prepare for your job interview by studying basic design principles and preparing answers to possible questions about them. Understanding some types of questions an interviewer may ask you can help you prepare your answers to speak efficiently and effectively and potentially obtain your dream job.

In this article, we discuss six example system design interview questions with sample answers to help you prepare with some tips.

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What is a system design interview?

A system design interview allows candidates, like programmers, designers, developers and software engineers, the opportunity to share their expertise in creating and developing applications and systems businesses can use. Interviewers can also determine your knowledge of elements of a system based on your responses to various questions. Generally, companies conduct this type of software engineering interview later in the hiring process. It's a trial to see how well you work on a team and your approach to problem-solving using open-ended questions to arrive at a helpful solution.

A system design interview analyzes your process of solving problems, using a company's primary tool for software, maintaining different types of documentation and creating designing systems to help clients. It's an opportunity to show the hiring manager and potential team you're a valuable asset and concretely display your skills and expertise.

Related: How To Become a Systems Designer (Plus Salary and Outlook)

System design interview questions with answers

These tech interviews all have different approaches and ask various questions to test your expertise and allow you the opportunity to demonstrate your qualifications. Here are six common system design interview questions a company's hiring manager may ask you:

1. How do you design a tinyURL system?

A tinyURL is an URL shortening service that allows users to enter a long URL and returns a shorter, unique URL which can minimize IP address exposure for increased privacy. A hiring manager might ask this to allow you to show your solid foundation in development. You can focus on other basics not listed in the example response, like how you create a unique ID for each URL, handle redirects and delete expired URLs using a web server.

Example: "When I worked for a public social network site, I created a simple system where every message had a 140-character limit. It also necessitated shortened URLs of about 30 characters. This tinyURL system is also useful when entering hyperlinks in e-mails or on a smartphone, where there's room for error. TinyURL is an excellent example of a hash table. This data structure associates keys with values and is a simple connections code. Using this basic 16-bit hash table, I optimized usability and met the system's needs."

Please note that the company mentioned in this article is not affiliated with Indeed.

2. How might you design a search engine?

Sometimes a specific department in a company requires search engines to locate an item or employee information systematically. Hiring managers look to see if you can tailor designs to a company's needs. You can detail some of the overall architecture and explain it, using the foundation below. You can also consider discussing relevant issues, such as website front-end performance, testing search engine improvements and integrating previous search data and trends in indexing.

Example: "I have worked on a project similar to this one. The search engine I was creating needed to work with keyword searches. My first step was building an indexer, so the crawler put web page links together and groups them or dumps them into sets. Then, the indexer ran as part of a reduced job to single things out. I set the crawl for H1 and H2 rather than H3s. After that, I checked outbound links to avoid spammers. Lastly, I checked the serving results to verify the design worked at optimal capacity and relevancy."

Related: What is a Search Engine Results Page (SERP)?

3. How do you design a web crawler, and when do you use it?

A crawler is a program designed to visit other sites and read them for information. System designers use this information to create entries for a search engine index. An interviewer may refer to it as a bot or spider. In your answer, show within your explanation you know the intricacies of web crawling.

Example: "I worked in the fashion industry, so the crawler scrapes data from a specific sector, like fashion. My first step was to integrate a URL dispatcher, a server that distributes seed URLs to multiple servers. Next, the crawl supervisor passed the URL to bots using the designed messaging queue. The spider extracted the data and loaded it into my file system. Next, the extract, transform and load (ETL) cleaned and reformatted the content to store it in the relational database. So, I crawled the web looking for and organizing the information needed."

Related: What Is a Web Crawler?: How They Work and How They Affect SEO

4. How do you design a shared drive?

Hiring managers ask how you design a drive to share files to explore algorithm basics and backgrounds. Before you begin, make sure you understand the purpose of the hypothetical task in the question. Knowing if the changes can register in real-time if locking is necessary and if it's required to be naturally convergent may help you give a complete answer.

Example: "This system works on differential synchronization. It's keeping two or more copies of the same document synchronized in real time so if someone changes one version, the same alteration happens on all the others. It's a complex challenge, but differential synchronization has horizontal scaling and fault tolerance. I did this for a client's in-house document sharing. They wanted real-time collaboration, so I used event passing as the locking or ownership approach can only allow the first one to open the document and make adjustments. This served the client well, as its employees were able to work collaboratively."

Related: 13 File-Sharing Tools for Professional Team Use

5. What is required to design a garbage collection system?

Garbage collection (GC) makes a system more efficient and ensures a Java system runs appropriately. GC also frees a programmer from having to do it manually. Hiring managers look to see if you know how to design the ins and outs of various real-world systems for data storage.

Example: "My client required a way to have more computer memory, but there was an issue with always having to go in and deal with memory deallocation. Garbage collection makes a system appear as if it has endless memory. What's happening is the system is re-purposing the memory. I set up their system so that if we reference an object or its recursive, it remains. Next, it goes through methodically and marks non-referenced items and sweeps them. This method with the void command helps to repurpose and free up memory. Now, my client has a faster system with less maintenance."

Related: What Is the .NET Framework? Overview, Components and Benefits

6. How do you design a recommendation system?

Recommendation systems help users find what they want more efficiently. They help clients and customers by offering alternatives and allowing for choice. Hiring managers inquire about this to see if you can create user-friendly and focused systems. In your answer, you can highlight your problem-analysis skills when discussing your experience with the recommendation system in the past.

Example: "One of my first and most loyal clients had an issue where their customers struggled with the user interface to find options on their website. A single user had to be exact in their search to find the product. I suggested implementing a recommendation system to help with customer satisfaction and sales. Using the prominent approach of collaborative filtering, I designed the system to weave an information tapestry to give our client's customers suggestions based on user similarity. The system became more user-friendly and produced a 10% increase in sales for my client."

Related: 7 Windows Communication Foundation (WCF) Interview Questions

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System design interview tips

As you consider your own responses to the standard system design interview questions above, here are some tips to help you feel more confident and prepared for your interview:

Use the STAR response technique

STAR is an acronym for situation, task, action and result. Formatting your responses using the STAR interview response technique is a strategy to help you craft answers that illustrate your knowledge and qualifications through specific experiences. Using this method, discuss an applicable situation, identify the task to complete, outline your actions and reveal the results of your efforts to demonstrate your skills to the interviewer.

Review the job description

Reviewing the job description to understand the role's specific requirements and details can help you prepare for your meeting with relevant answers or follow-up questions regarding your potential responsibilities. You can also use the duties and skills listed in the description as talking points in the interview.

Related: Job Specification vs. Job Description Explained

Know the company

Research the company before the interview to learn about its mission and past projects. Knowing the basics and more about an organization can help you facilitate the conversation and ask direct questions, which may impress the hiring manager and increase your chances of getting hired. Research can also help you determine if you're the right fit for the company culture.

Additionally, at the end of an interview, the hiring manager may ask if you have any other questions you have for them. It's valuable to prepare one to two questions to ask, and one of those can include a query from your own list of questions about the organization. For example, you can ask how previous projects aligned with the company's mission.

Related: 10 Things You Should Know About a Company Before Your Interview

Practice is essential

The opportunity to go through the design interview process repeatedly while applying these tips may help you project confidence and discuss key concepts with ease. Additionally, the familiarity you have with the topic can reveal your qualifications. Spend time practicing interview question answers with a friend or family member because they may provide helpful feedback you can apply to your next meeting. You may also practice your responses in front of a mirror.

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