System Design Interview Guide: 10+ Must-Know Topics and Concepts Quiz

Sharpen your understanding of key system design patterns and concepts vital for acing real-world technical interviews in 2026. Assess your knowledge of practical, foundational system design strategies and architecture principles.

1. Understanding Load Balancers

   What is the main purpose of using a load balancer in a distributed system?

   1. To permanently store application data
   2. To manage file compression in the network
   3. To distribute incoming requests efficiently across multiple servers
   4. To provide authentication for system users

   Explanation: A load balancer's primary role is to evenly distribute traffic among servers to improve availability and prevent any single server from becoming a bottleneck. It does not handle data storage, manage user authentication, or deal with file compression, which are addressed by other system components.

2. Role of Caching

   Why is caching often used as an early optimization in large-scale system design?

   1. To automate deployment processes
   2. To reduce database read load and improve response times
   3. To improve data encryption between services
   4. To increase the number of supported programming languages

   Explanation: Caching stores frequently accessed data in a fast layer, reducing database queries and speeding up user experiences. While important, encryption, multi-language support, and deployment automation are unrelated to caching's main function in system optimization.

3. APIs and Extensibility

   How does designing a system with clear and versioned APIs contribute to extensibility?

   1. It guarantees unlimited storage capacity
   2. It eliminates the need for monitoring tools
   3. It encrypts all data automatically
   4. It allows independent updates and feature additions without breaking existing integrations

   Explanation: Versioned APIs support backward compatibility, making it easier to add features or change implementations without disrupting current users. Versioning does not provide encryption, storage scaling, or monitoring capabilities.

4. Comparing Databases

   When choosing between a relational database and a NoSQL store, which factor is most important to consider?

   1. The colors used in the user interface
   2. The brand of server hardware
   3. The website's logo design
   4. The consistency and structure needs of the data

   Explanation: Relational databases work best for highly structured data requiring consistency, while NoSQL databases suit flexible or large-scale data scenarios. Interface color, hardware brand, and logo design do not influence database selection.

5. Applying CAP Theorem

   What does the CAP theorem state about distributed data stores?

   1. A distributed system will always be both 100% secure and fast
   2. A database can scale horizontally without any tradeoffs
   3. A distributed system can simultaneously provide only two out of three: consistency, availability, and partition tolerance
   4. All distributed systems must use NoSQL databases

   Explanation: The CAP theorem explains that under network partition, a distributed system must trade off between consistency and availability. Security, database choice, and unlimited scalability are not aspects described by the theorem.