What is expected in system design interview?

In a system design interview, the expectation is to evaluate a candidate's ability to design complex and scalable software systems. These interviews test your understanding of architectural principles, your problem-solving skills, and your ability to handle real-world engineering challenges. Here’s what is typically expected during a system design interview:

1. Understanding of Key System Design Principles

• Scalability: Can you design systems that efficiently handle growth in terms of data, traffic, or complexity?
• Reliability: Does your design ensure that the system can run continuously without failure and can recover when failures occur?
• Efficiency: Are your solutions optimized for speed and resource usage?
• Maintainability: Is your system easy to operate, maintain, and update?
• Security: Have you considered potential security risks and implemented measures to mitigate them?

2. Ability to Handle Open-Ended Problems

• System design questions are often broad and open-ended without a single correct answer. You're expected to engage in a dialogue with the interviewer, ask clarifying questions, and iteratively refine your design.

3. Effective Communication

• Clarity: You should be able to clearly explain your ideas, design choices, and trade-offs.
• Detail: While maintaining a high-level overview, you should also dive into critical details of specific components when necessary.
• Visualization: Using diagrams or whiteboarding effectively to illustrate system components and interactions is crucial.

4. Practical Application of Theoretical Knowledge

• You should be able to apply theoretical knowledge to practical scenarios, demonstrating how to use technologies and architectures to solve real problems. This includes selecting appropriate databases, implementing caching mechanisms, and choosing between different data handling techniques.

5. Component Design

• Modularity: Designing systems with clear, well-defined components or modules that interact with each other.
• API Design: Designing efficient and secure APIs that enable different software components to communicate effectively.
• Data Management: Making decisions on data storage, retrieval, and update mechanisms, including choices about database types and structures.

6. Consideration of Non-functional Requirements

• Besides the functional aspects of a system, you're expected to consider non-functional requirements like scalability, performance, security, and compliance.

7. Handling Trade-offs and Making Decisions

• Demonstrating the ability to make informed decisions by considering various trade-offs between competing factors such as cost, speed, complexity, and future scalability.

8. Iterative Approach

• Showing how you refine and evolve your system design based on new information or feedback from the interviewer.

9. Technical Depth and Breadth

• Displaying a good grasp across various technical domains, which may include cloud services, front-end technologies, back-end servers, networking issues, and more.

Preparation Tips

• Study Well-Known Architectures: Learn from existing large-scale systems by studying their architectures and the rationale behind certain design decisions.
• Practice Designing Systems: Regularly practice designing systems from scratch for a variety of requirements and constraints.
• Mock Interviews: Engage in mock interviews to get used to the format and to receive feedback on your approach and communication skills.
• Read Books and Take Courses: Books like “Designing Data-Intensive Applications” by Martin Kleppmann and online courses like Grokking the System Design Interview are excellent resources.

Conclusion

A system design interview is a test of your overall ability to design systems that are robust, scalable, and efficient. The expectation is not only for you to demonstrate technical proficiency but also to show how you approach complex problems, make decisions, and communicate effectively.