System design interviews are critical to most software engineering roles, but they’re also the hardest to prepare for. These interviews assess a candidate’s ability to architect scalable and efficient systems.
Most candidates struggle with System Design interviews for two reasons:
- You typically don’t get practice with system design in personal projects or school assignments. The scale of users and data simply isn’t there for building sophisticated systems that are discussed in interviews.
- Even if you have meaningful professional experience, most engineers are not actually architecting systems. It’s entirely possible to spend 3-4 years at a company like Google and be a “feature-factory” instead of someone who actually influences the work of many engineers via system design decisions.
As a result, many engineers are left to their own devices when it comes to their preparation strategy. In this blog post, I’ll share the insights from my conversation with an engineer who has evaluated over 1,000 System Design interviews. She shares the most common ways that Software Engineers fail the System Design round during interviews. Here’s a portion of my conversation with her:
Understanding System Design Interviews
Before diving into the common pitfalls, let’s talk about what system design interviews entail. Unlike traditional coding interviews that focus on algorithms and data structures, system design interviews require candidates to demonstrate their ability to design complex systems. This includes considerations for scalability, reliability, maintainability, and performance.
Candidates are often presented with a high-level problem statement, such as designing a URL shortening service or a social media platform. The interviewer expects the candidate to break down the problem, identify key components, and articulate their design choices clearly.
Common Pitfalls in System Design Interviews
1. Lack of Clarity in Requirements
One of the most significant mistakes candidates make is jumping into the design without fully understanding the requirements. Candidates often assume they know what the interviewer wants, leading to misaligned designs.
Solution: Clarify requirements before diving into the design. You should ask questions to uncover the scope of the prompt, including:
- What are the primary use cases?
- Who are the end-users?
- What are the expected traffic patterns?
- Are there any specific constraints or requirements?
By taking the time to clarify these points, you’ll ensure you’re on the right track and avoid unnecessary rework later in the interview.
2. Ignoring Scalability
Another common pitfall is failing to consider scalability from the outset. Many candidates design systems that work for small datasets but struggle to handle larger loads. This oversight can lead to designs that are not viable in real-world scenarios.
Solution: Thinking about scalability early in the design process:
- How the system will handle increased traffic.
- The potential need for load balancing.
- Data partitioning strategies.
- Caching mechanisms to improve performance.
By incorporating scalability into the initial design, candidates can demonstrate their foresight and understanding of real-world applications.
3. Overcomplicating the Design
You should be drawing boxes for various components in your system design, but don’t overdo it! Don’t fall into the trap of overcomplicating your designs. This can lead to confusion and make it difficult for the interviewer to follow the candidate’s thought process.
Solution: Start with a simple design and gradually add complexity as needed. A good approach is to:
- Begin with a high-level overview of the system.
- Identify core components and their interactions.
- Introduce additional features or optimizations only if time permits.
This method allows candidates to communicate their ideas clearly and ensures that the interviewer can follow along without getting lost in unnecessary details.
4. Neglecting Trade-offs
In system design, trade-offs are inevitable. Candidates often fail to acknowledge the trade-offs involved in their design choices, which can lead to unrealistic expectations about system performance and capabilities.
Solution: The course teaches candidates to articulate the trade-offs they make during the design process. For example, if a candidate chooses a NoSQL database for its scalability, they should also mention the potential downsides, such as eventual consistency or the lack of complex querying capabilities.
By discussing trade-offs, candidates demonstrate their critical thinking skills and their ability to make informed decisions based on the specific requirements of the system.
5. Failing to Consider Non-Functional Requirements
While functional requirements are often the focus of system design interviews, non-functional requirements such as security, reliability, and maintainability are equally important. Candidates frequently overlook these aspects, leading to designs that may function well but are not robust or secure.
Solution: Address non-functional requirements throughout the design process:
- How to ensure data security and privacy.
- Strategies for fault tolerance and disaster recovery.
- Approaches to maintainability and ease of deployment.
By incorporating these considerations, candidates can present a more comprehensive and realistic system design.
6. Poor Communication Skills
Even the best designs can fall flat if candidates cannot communicate their ideas effectively. Many candidates struggle to articulate their thought process, leading to misunderstandings and confusion during the interview.
Solution: Try these tactics to immediately improve your communication skills during system design interviews:
- Speak clearly and confidently.
- Use diagrams to illustrate their designs.
- Summarize key points to reinforce understanding.
Practicing these skills can help candidates convey their ideas more effectively and engage the interviewer in a productive discussion.
7. Lack of Practice
Finally, many candidates underestimate the importance of practice. System design interviews require a different skill set than traditional coding interviews, and candidates who do not practice will be unprepared.
Solution: Use mock interviews and practice designing systems regularly. This can involve:
- Collaborating with peers to simulate interview scenarios.
- Reviewing common system design problems and solutions.
- Seeking feedback to identify areas for improvement.
Conclusion
System design interviews can be daunting, but with the right preparation and awareness of common pitfalls, you can significantly improve your pass rate. Taro’s course, “The Top Ways People Fail System Design Interviews,” goes into detail about the strategies we covered.
By focusing on clarifying requirements, considering scalability, avoiding overcomplication, acknowledging trade-offs, addressing non-functional requirements, improving communication skills, and committing to practice, candidates can approach their system design interviews with confidence and clarity.
For any role beyond entry-level, you will likely have some element of a System Design Interview in your job search process. Whether you’re preparing for your first system design interview or you’re an industry veteran, let us know what has worked for you.
