Roadmap to Prepare for a System Design Interview: A Beginner’s Guide

7 min readApr 29, 2024

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Are you gearing up for a System Design interview and wondering how to prepare effectively? System Design interviews assess your ability to architect complex systems, make design decisions, and communicate your ideas clearly. Whether you’re a novice or have some experience, having a structured roadmap can significantly boost your preparation. Here’s a beginner-friendly guide to help you navigate through the process:

To effectively prepare for System Design Interviews, it’s crucial to first understand the systematic process involved in designing complex systems.

1. Requirements Analysis: The process begins with a thorough understanding and analysis of requirements. The requirements can be categorized into functional requirements that describe specific features and functionalities and non-functional that specify qualities and attributes like performance and reliability.

2. Resource Estimation: After grasping the requirements, the next step involves estimating the necessary resources, including the number of servers, storage capacity, and network bandwidth required to fulfill both functional and non-functional requirements.

3. Design Elements Selection: Common design elements such as load balancers, Content Delivery Networks (CDNs), Domain Name Systems (DNS), distributed caches, and messaging systems offer pre-designed solutions to typical challenges in distributed system design. Incorporating these elements streamlines the design process and avoids reinventing the wheel.

4. Abstract High-Level Design: In this step you develop an abstract high-level design that identifies various system components while adhering to the single responsibility principle. This step provides an overview of the system architecture and helps in understanding the interactions between different components.

5. API Design: Define the various APIs and their communication protocols to ensure seamless interaction between different parts of the system, aligning with both functional and non-functional requirements. Determine the necessary web communication and data fetch patterns to facilitate interactions between system components effectively.

If you are new to APIs, you can learn about which architecture is recommended, monolith or service-based, here.

6. Data Modeling (Optional): While data modeling may not always be a focal point in system design interviews, it’s essential to understand its principles and techniques. Familiarize yourself with data modeling concepts and be prepared to apply them if required during the interview process.

Finally, evaluate the design to ensure it meets all agreed-upon requirements.

Use any remaining interview time to address any additional aspects as needed, consulting with the interviewer for guidance. Throughout the system design discussion, stick to the scope agreed in the beginning and bring to the discussion various distributed system concepts knowledge you have.

Now, let’s explore what to learn in order to excel at each step of the system design process.

Understand the Fundamentals

Functional requirements detail the specific features and functionalities needed to meet user needs. And non-functional requirements describe the desired qualities of the system, like performance and reliability.

To create efficient designs, it’s crucial to grasp fundamental distributed systems concepts. Familiarize yourself with key terms including scalability, reliability, availability, software performance, various performance metrics, fault tolerance, and maintainability.

System design often involves making trade-offs between different factors such as performance, cost, complexity, and ease of maintenance. Optimizing one aspect of a system may come at the expense of others.

Master the art of articulating system design trade-offs and hone your decision-making abilities.

Explore various trade-offs including:

1. Strong versus Eventual Consistency

2. Balancing Latency against Throughput

3. Weighing Batch Processing against Stream Processing

4. Evaluating Load Balancer versus API Gateway

5. Comparing Proxy with Reverse Proxy

6. Deciding between SQL and NoSQL databases

7. Choosing between REST and RPC for communication protocols

8. Exploring Polling, Long-Polling, and Webhooks for real-time updates

9. Assessing Serverless Architecture versus Traditional Server-based setups

10. Differentiating Stateful from Stateless Architecture paradigms

Back-of-the-envelope calculations

Back-of-the-envelope calculations refer to quick, rough estimates or calculations done using simplified assumptions and basic principles.

Back-of-the-envelope calculations are indispensable tools for system design interview preparation, enabling you to assess, validate, and communicate your design decisions effectively. They help you approach design problems systematically, think critically about scalability, performance, and resource requirements, and ultimately present well-thought-out solutions to the interviewer.

Some example could be:

1. The number of concurrent TCP connections a server can support.

2. The number of requests per second (RPS) a web, database or cache server can handle.

3. The storage and network bandwidth requirements of a service.

Building Blocks of System Design

In preparing for system design interviews, it’s crucial to grasp commonly-used design elements like load balancers, which play a vital role in implementing both functional and non-functional requirements. These building blocks form the foundation of system architecture and understanding their functionality is essential for success in system design interviews.

Below is the exhaustive list of necessary building blocks.

1. Domain Name System: DNS, or Domain Name System, is a decentralized system that translates human-readable domain names into machine-readable IP addresses, enabling users to access websites and services on the internet.

2. Load Balancers: A load balancer is used to fairly distribute incoming clients’ requests among a pool of available servers. It also reduces load and can bypass failed servers.

3. API Gateway: An API Gateway is a centralized service that acts as an entry point for all client requests to backend microservices, providing features such as request routing, authentication, authorization, and rate limiting.

4. Databases: Good understanding of database types (SQL, NoSQL, Graph, etc), replication, and partitioning. Knowledge of CAP and PACELC theorems, various consistency models is highly sought after. Explore well known databases like Cassandra, HBase, CouchBase, MongoDB, etc and the use cases where their usage is suggested.

5. Content Delivery Network: A content delivery network (CDN) is used to keep popular media content such as videos, images, audio, and webpages. It efficiently delivers content to end users while reducing latency and burden on the data centers.

6. Distributed Caching: In a distributed caching system multiple cache servers coordinate to store frequently accessed data.

7. Distributed Messaging Queue: This building block is used between interacting entities called producers and consumers. It helps decouple producers and consumers, results in independent scalability, and enhances reliability.

8. Publish-Subscribe System: This building block focuses on an asynchronous service-to-service communication method called a pub-sub system. It is popular in serverless, microservices architectures and data processing systems.

9. Blob Store: This building block focuses on a storage solution for unstructured data — for example, multimedia files and binary executables.

Apart from the above building blocks, several other design elements commonly feature in system design discussions.

10. Sequencer or Unique ID Generator: In this building block, the focus is on the design of a unique IDs generator with a major focus on maintaining causality.

11. Service Monitoring: Monitoring systems are critical in distributed systems because they help analyze the system and alert the stakeholders if a problem occurs. Monitoring is often useful to get early warning systems so that system administrators can act ahead of an impending problem becoming a huge issue. Typically there are two monitoring systems, one for the server-side and the other for client-side errors.

12. Rate Limiter: Rate Limiter is a system that throttles incoming requests for a service based on the predefined limit. It is generally used as a defensive layer for services to avoid their excessive usage-whether intended or unintended.

13. Distributed Search: A search system takes a query from a user and returns relevant content in a few seconds or less. This building block focuses on the three integral components: crawl, index, and search.

14. Distributed Logging: Logging is an I/O intensive operation that is time-consuming and slow. Distributed Logging is a system that allows services in a distributed system to log their events efficiently. The system needs to be scalable and reliable.

15. Distributed Task Scheduling: A distributed task scheduler system mediates between tasks and resources. It intelligently allocates resources to tasks to meet task-level and system-level goals. It’s often used to offload background processing to be completed asynchronously.

16. Sharded Counters: This building block demonstrates an efficient distributed counting system to deal with millions of concurrent read/write requests, such as likes on a celebrity’s tweet.

By familiarizing yourself with these building blocks and their practical applications, you’ll be well-equipped to tackle system design interview questions and design robust, scalable systems for real-world scenarios.

API Design

API design is an essential aspect of system design, particularly in the context of designing scalable and efficient distributed systems. Understanding how to design robust and user-friendly APIs can greatly enhance the overall architecture of a system, improve developer productivity, and ensure smooth integration between different components.

A good grasp of network protocols, HTTP based web and data communication, Client-Server communication, API architecture styles, HTTP/1.1, HTTP/2, and HTTP/3, Security, etc.

Data Modeling

Designing the database schema and data storage mechanisms for the system, including database schema design, data partitioning strategies, indexing, caching, and data consistency mechanisms.

Practice and Feedback

Practicing system design problems for commonly asked problems like designing YouTube, WhatsApp, and seek feedback on your approach from online resources or mock interviews.

Listed below are frequently asked system design problems:

1. YouTube

2. Quora

3. Google Maps

4. URL Shortening Service

5. Uber

6. Twitter

7. Yelp

8. WhatsApp

9. Web Crawler

10. TypeAhead Suggestion

In conclusion, preparing for a System Design interview requires a systematic approach to understand complex concepts and effectively communicate solutions. By mastering the fundamentals, grasping the significance of trade-offs, and familiarizing oneself with key building blocks, candidates can confidently navigate through interview questions. Additionally, focusing on API design and data modeling enhances the overall architecture and scalability of systems. With a structured roadmap and diligent practice, candidates can excel in System Design interviews and design robust, scalable systems for real-world scenarios.

Must Read for Continuous Learning

Roadmap to Prepare for a System Design Interview: A Beginner’s Guide

Must Read for Continuous Learning

Written by Roopa Kushtagi