System Design Interview Guide

You’ve received an interview call from your dream company, bringing you one step closer to your dream job. It’s not long before your joy gives way to anxiety when you realize you have a challenging task ahead of you — clearing the system design interview. An interview that could be the career-defining launchpad you’ve been searching for.  

System design interviews at FAANG and top tech companies are known to be very challenging. It’s natural to feel a sense of apprehension over it. 

The perfect antithesis to this is structured preparation. Sound preparation is what will help you perform at your best. Strong interview performance is exactly what you need to deliver to impress interviewers at your system design interview.

It’s a good time to work in system design. According to Tech Republic, system design job volumes and salaries are projected to grow right through to the year 2029. The software development industry is slated to grow by 22%, as 316,000 jobs are expected to be added. 

The top-paying metropolitan cities for system design jobs in the U.S. are San Jose, San Francisco, Seattle, New York, and Battle Creek. 

Facebook, Google, Amazon, Airbnb, and LinkedIn are some of the top companies that conduct system design interviews as part of their recruitment processes for tech roles. 

This article will cover key aspects to be considered when preparing for a system design interview:

• What Is System Design?
• Designing a System 
• System Design Interview Questions and Use Cases
• System Design Interview Preparation Tips
• System Design Interview Tips
• How to Approach to System Design Interviews

What Is System Design?

System Design is the process of defining and designing the architecture, modules, interfaces, nature of data, and data flows in a system. The main objective of system design is to build a coherent and logical system that directly fulfills the purpose it was built for.  

Always remember — the main purpose of system design is to solve a problem.

Your system design should be able to solve a given problem using the shortest possible route. The length of the path of your design will define the system's efficacy and cost-efficiency. Tech recruiters look for creative problem-solvers.  

Basic Concepts of System Design 

Here, we take you through some important system design topics you should prepare on: 

Scalability: 

Scalability defines the range of capabilities in which a system can be used. Vertical Scaling refers to powering up the system by adding more machines to an existing system. In contrast, Horizontal scaling, also referred to as scaling out, means adding resources so that the defined ceiling limit remains untouched. 

Load Balancing and Caching:  

A load balancer can be hardware or software. Its main purpose is to increase the reliability and performance of the system by distributing the load over multiple computing nodes.  

Caching is the process of storing copies of application data that is frequently used. As a result, caching improves throughput, computing costs, and data retrieval time. 

Shared Storage: 

Shared storage is a centralized storage medium that multiple users can access. A shared storage system will have multiple access ports, and sessions can be tracked and identified. 

Data Replication: 

Data replication is storing data in more than one location. This allows the system to reduce network latency, decrease fault-toleration issues, and increase availability. 

Network Protocols And Proxies: 

Properly defined protocols in a network infrastructure simplify data flow and improve throughput. In addition, network protocols are the key to how a system's components interact. 

Databases: 

A database is where a system's data can be stored, updated, deleted, and returned for query. It is essential to mention the CAP Theorem here:

• Consistency: Every node should respond with the most recent version of the data.  
• Availability: Any node should be able to send a response.  
• Partition Tolerance: The system should continue to run even if communication between two or more nodes is broken. 

Performance Measures: 

Latency, throughput, and availability are some of the measures based on which the performance of a system is evaluated. 

• Latency: The amount of time taken for a message to be delivered. It is measured in milliseconds (ms).  
• Throughput: This is the amount of data delivered successfully in a given time. It is measured in bits per second (bps). 
• Availability: This is the amount of time a system remains available. It is the ratio of Uptime and Uptime + Downtime. 

Additional system design topics to prepare:

• Leader-Election Algorithm: How a leader-less node cluster communicates to elect the optimal leader.  
• Queues and Pub-Sub: Mechanisms that provide an intermediary to the communication model of the system so that messages can be transmitted asynchronously.
• Sharding: Scaling the system horizontally by breaking up the system into smaller fragments called shards. 
• Polling, SSE, and WebSocket: Latest protocols that considerably improve the memory efficiency and speed of the data streams.  

Studying these system design concepts, in detail, will enable you to define the basic architecture of any system effortlessly.  

Designing a System 

The main elements of any system design are:

Elemental Requirements:

Ask your interviewer clarifying questions to ensure you’ve understood the goals of the system you will be designing. 

Recruiters look for empathic candidates capable of designing a system that achieves its goals. Finding out the system's constraints will help you narrow down and focus on the system goals. 

Requirements can be: 

• Functional: The specific system input and output deliverable that is expected from the system design. 
• Non–Functional: Parameters such as scalability, performance, security, reliability based on which the system's value is determined. 

Architectural Components:

Define the length and scale of architectural components like storage capacity prognosis, frequency of timeline generation, hardware support, and network bandwidth usage. 

Data Flow:

Define how data will flow between various components of the system and identify critical data points. Start by working on a data flow model when designing a system. Select the database best suited for your system; SQL and NoSQL are popular choices.  

Segregated Component Design:

Instead of working on the whole system at once, break it down into a block diagram of manageable components. This will ensure you pay attention to the details as well as the big picture. You will have to extend the design to create specific components.  

A System Needs Details 

It is now time to work in detail on the components you identified. 

You may want to use load balancing, service and data replication, data partitioning, message queues, caching, encryption, and other such components. 

Conduct a trade-off analysis to find out the optimal way to utilize these components. Identify the different ways in which you can approach a problem. 

Remember to explain to your interviewer why you selected a particular approach.  

Predicting Bottlenecks 

Identify possible bottlenecks to fool-proof your system design. Ensure there are multiple copies of running services and sufficient data replicas so that a few failures do not snowball into a complete system shutdown.  

Hot Tip: Most organizations cite cybersecurity as a necessary skill for system design roles. Ensure your system design is built around security loopholes and can withstand possible security threats.  

System Design Interview Questions and Use Cases

Once you have a good grip on the basics of system design, you should practice answering the most common question asked in system design interviews – “How would you design a system?”  

The kind of system you are asked to design depends on the company you are interviewing for. While Google System Design interview questions differ from Amazon System Design interview questions, you can still prepare a basic foundation, then research the company's use cases. 

Below are some of the most common system design interview questions and how to answer them:

• How would you design a search engine? 

Define the overall architecture based on your knowledge of system design basics. Pay attention to keyword searches and where you want to place your crawler for indexing links that appear in a search. Calculate and analyze the number of links for each website. To avoid spam, check outbound links. 

• How would you design a shared drive? 

Shared Drive questions are a good test of algorithm basics. Ask if the system will be working in real-time and if locking would be necessary. 

Focus on differential synchronization, that is, synchronizing two or more copies of a document in real-time. Use event-passing to allow real-time collaboration. 

• How would you design Twitter? 

Social networking platforms are a popular question in system design interviews. Pay attention to onboarding flow, user-follow flow, tweet flow, scalability, and read-to-write ratio. 

• How would you design a video streaming system?  

A video streaming system will need a recommendation service. It should also be able to read different formats. Focus on how you can simplify the process of onboarding new content since it is done regularly. 

• How would you design a messaging system? 

Messaging systems like Whatsapp heavily depend on the right memory allocation. Also, brush up on HTTP, WebSocket, and long pooling. 

• How would you design a vaccine rollout system? 

Often, interviewers are keen to assess your capabilities in solving current world problems. 

In this case, key points to consider will be: creating unique IDs to prevent overlapping, a synchronized update system, a simplified user interface, and appropriate memory allocation. 

Recommended Reading:
Google System Design Interview Questions
Facebook System Design Interview Questions
Amazon System Design Interview Questions

Additional use cases/question topics to prepare for your System Design interview are:

• Web Crawler 
• TinyURL System 
• Typeahead Suggestion Service - Autocomplete 
• API Rate Limiter 
• Social Media System – Facebook, Instagram, Twitter 
• Cloud Services – Google Drive, Google Docs, Amazon S3 
• Video Streaming – Netflix, Prime, Hulu 
• Online shopping – Amazon, Walmart, Airbnb, eBay 
• Transportation – Uber, Lyft 
• Mapping System – Google Maps 
• Video Conferencing – Zoom, Google Meet, Skype 
• Review System – Yelp, TripAdvisor, DoorDash 
• Dating Platforms – Tinder, Bumble, Hinge 
• Payment - PayPal 
• Gaming - Online Multiplayer  
• Ticket Management System – Entertainment, Hotels, Airlines 
• Library Management System 

System Design Interview Tips

Before the interview:

• Ensure you understand the job role and job description. 
• Research the company and its values. 
• Map out your interview journey and the steps you will have to take to reach your goal. 
• Identify the most common system design interview questions. 
• Extensively study use cases and the different possible approaches. 
• Practice designing with fellow system designers and other professionals from the field. 
• Practice thinking like a problem-solver. 
• Prepare questions for the interviewer.
• Keep yourself updated about the latest breakthroughs in system design. 
• Evaluate your strengths and qualifications and how they apply to the system design role. 

During the interview:

• Ask a lot of clarifying questions to define the needs and goals of the system; also, define the requirements and constraints. 
• Don’t get into the details of the system design prematurely. 
• Intermittently, explain your approach and process to the interviewer 
• Utilize the STAR technique to showcase your knowledge and experience. STAR stands for Situation, Task, Action, and Result. Use it to explain situations and the skills you applied to resolve these situations. 
• Leverage your background, experience, and skills to show the interviewer you can develop unique solutions to the given system design problem. 
• Don’t use too many buzz words when answering questions.
• Give yourself a pep talk before the interview to calm your nerves.
• Calm yourself before the interview; perform deep breathing or any form of meditation that works for you. 

For more system design interview tips, click here.

How to Approach System Design Interviews 

Whether you’re interviewing for the position of a coding engineer or a software developer, the role of a system design engineer is a unique one. 

Being a system design engineer is an opportunity to solve a problem that affects many people. As a system design engineer, you get to influence lives and make life easier through the systems you build. 

Understand the values of the company you are interviewing for. Assess the magnitude of impact that the systems you design in the future will have. This approach will give you a new perspective on the job you are applying for. It will also help you meet the aptitude and skill levels interviewers expect of candidates. 

Are You Ready to Nail Your Next Tech Interview?

Since its inception in 2014, Interview Kickstart has helped thousands of experienced engineers realize their true calling. We aim to help engineers get better acquainted with the intricacies of their chosen field and provide them with all the guidance they need to clear interviews with tech giants. 

Knowing very well that clearing an interview requires much more than sound technical knowledge, we train you in a manner that helps you develop a winner's stride. IK is your golden ticket to land the job you deserve.

Want to learn more? Sign up for our FREE webinar on how to nail your next tech interview.