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Introduction to the System Design Interview

System design interviews are one of the most interesting—and challenging—parts of the engineering interview process. These questions are intentionally open-ended, like “Design Netflix” or “Design a Rate Limiter.” It’s on you to lead the conversation, define requirements, and demonstrate your knowledge under pressure. Practicing these interviews the right way can definitely improve your chances of landing the job at the level you deserve.

After teaching thousands of engineers how to prepare for these interviews, we've found that the best way to approach system design is not by trying to memorize dozens of unrelated problems in isolation.

The secret that sets top engineers apart from everyone else is understanding architectural patterns. That's why we've re-organized this course around the most common patterns, from distributed storage to event-driven systems. Each pattern consists of a family of systems with shared components, scaling strategies, and concepts. Once you recognize which pattern(s) a system belongs to, you can apply them to any question that fits the mold.

How this course is organized

The goal of this course is to teach you everything you need to know for your upcoming interview. Here's what it includes:

  1. The interview format. We'll give you the complete framework for how to answer any system design question, advice on how to lead the conversation like a senior engineer, and tips on using a (digital) whiteboard. We also review the exact interview format and grading rubric used by top companies like Google, Meta, and OpenAI.

  2. System design patterns. You'll learn the fundamental architectural patterns, starting from essential CRUD architecture and building up to complex agentic AI systems. Each pattern explains the components involved, related interview questions, and deep dives to know about how each system scales and fails.

  3. Example interview questions. We include real interview questions asked at top companies, with mock interview videos featuring experienced engineers from these companies. Each problem also comes with a written breakdown of the problem that you can study at your own pace, showing multiple valid approaches and deep dive questions you can expect to be asked.

Last but not least, the Appendix reviews all the fundamentals that are assumed throughout the course. This includes refreshers on key concepts like caching strategies, load balancing, and database sharding. We link to these concepts throughout the course wherever they're used.

Where to start

You don't have to go top to bottom. Pick the entry point that matches where you are.

If you are...Start here
JuniorReview the course in order, focusing on the framework and rubric lessons first. Watch a few mocks to get a sense of the format.
Mid-levelReview the framework, core patterns, and appendix concepts that are unfamiliar.
Senior / StaffPrioritize studying problems that you expect to be asked about. Focus on deep dives and tradeoff discussions with an eye for how you'd improve each answer.
Short on timeSkim the Framework, then go to the module most relevant to your target role/company.

How to practice

Reading about system design will only take you so far. The skill you're building is thinking on your feet while explaining yourself clearly, and that only comes from reps.

When you're ready to practice, here are two options:

  1. Peer-to-peer mock interviews, where you practice with other engineers preparing for the same interviews.
  2. AI mock interviews, where you can try a full system design question on demand and get feedback whenever you want to practice.
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