What are the key topics to ace a system design interview?

Key takeaways:

• Grasp foundational topics in distributed systems, computer networking, data structures, and algorithms; these are crucial for understanding system architecture.

• Be well versed in common system design components like load balancers, databases, and messaging queues, as they form the backbone of most systems.

• Balancing scalability, consistency, and latency often requires trade-offs; recognizing these is key to effective design decisions.

• Communicate the reasoning behind your choices, consider alternatives, and discuss trade-offs to demonstrate critical thinking and adaptability.

• Effective communication and a structured approach, such as the RESHADED framework, can help navigate complex and open-ended questions in system design interviews.

System Design interviews are becoming increasingly popular, especially for roles that involve building complex applications.

These interviews help assess a candidate’s ability to not just write code but to think critically about how different components interact to create a scalable and reliable system. While the core concepts are important for all software engineers, the depth and focus of these interviews can vary based on the specific role.

System design interview key concepts

Unlike typical interviews, system design interviews demand a higher degree of skill. The sections below explain some key elements to prepare for the system design interview.

The basics

It is imperative to develop a fundamental theoretical knowledge of various domains such as:

• Distributed systems

• Computer networking

• Programming fundamentals

• Operating systems

• Data structures and algorithms

Next, we need to familiarize ourselves with the core structure of the System Design interview. You can see that below:

Designing systems is an advanced practice that cannot be perfected without the basics.

Core components

Other than specialized components within a particular system, there are basic components that are a part of almost every system. A candidate should be able to identify their use and placement within the design. Examples of such components are:

• Load balancers

• Messaging queues

• Rate limiters

• Databases

• Blob stores, and so on.

Learning about these components and how we can utilize them when designing systems is a surefire way to ensure that you can effectively attempt a System Design interview.

Non-functional requirement trade-offs

Non-functional requirements are another important aspect of system design. The trouble is that achieving one may lead to compromise on another. For example, strong consistency may lead to degradation in performance.

Here are some of the most common trade-offs we need to consider.

Soft skills

Soft skills are required in addition to technical topics because the candidate must acquire functional requirements for designing a system.

System design interviews are more of a discussion toward a solution than simple question-and-answer sessions. If the candidate has an adequate level of communication skills, they will be able to ask efficient clarification questions.

Justifying design decisions

In a system design interview, it's not enough to simply present a solution. You need to be able to explain why you made specific design choices.

Clearly articulating your reasoning demonstrates a deep understanding of the problem, the trade-offs involved, and your ability to make informed decisions. This is where justifying your design decisions becomes crucial.

Here's how we can effectively justify our design choices:

1. Connect to requirements:

• Explicitly link the decisions back to the initial requirements. For example, if you chose a specific database because it offers high availability, explain how that aligns with the requirement for minimal downtime.

• Address both functional and non-functional requirements. Show how your design fulfills the core functionality while also meeting performance, scalability, and reliability goals.

2. Consider alternatives:

• Briefly mention other options you considered. This shows we've explored different approaches and made a conscious decision based on the specific needs.

• Explain why you ruled out those alternatives. Highlight the limitations or drawbacks that led you to choose the current design.

3. Explain the trade-offs:

• Acknowledge that no solution is perfect. Discuss the advantages and disadvantages of the chosen approach compared to alternatives.

• Be transparent about the compromises you made. For instance, if we prioritized consistency over latency, we should explain why that trade-off was appropriate in this context.

4. Provide concrete examples:

• Use real-world examples or scenarios to illustrate your points. If discussing caching, explain how it would improve response times for specific user actions.

• Quantify your arguments whenever possible. Instead of saying, "It will be faster," say, "We expect a 20% reduction in query latency."

5. Be open to feedback:

• Welcome questions and challenges from the interviewer. This is an opportunity to further demonstrate your understanding and adaptability.

• Be prepared to revise your design based on new information or insights. Flexibility and a willingness to learn are highly valued in system design.

System Design interview strategy

Different system design problems must be tackled.

Interviewers often ask design questions that are unfamiliar to candidates. To handle these effectively, a structured approach is helpful. One such method is the Reshaded mnemonic. Regardless of the problem, candidates should follow each step outlined below.

Designing a system is both an art and a science. It takes years of experience and design practice. Perfecting the points listed above makes it easy to take System Design interviews.