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Welcome to the System Design Interview Prep lesson — a practical, beginner-friendly course that teaches a clear, repeatable approach to solving system design problems under interview constraints. This lesson is designed for absolute beginners with little or no system design experience. System design interviews require fast, structured thinking about components, trade-offs, scalability, and real-world constraints. This course gives you a six-step framework to organize your answers, practice problems, and hands-on labs to implement key components. What you’ll gain from this lesson:
  • A reproducible framework to structure interview responses.
  • Practical heuristics for making trade-offs under time pressure.
  • Hands-on experience implementing common building blocks used in interviews.
  • Sample solutions for common interview problems like URL shorteners and news feeds.

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Six-step Framework

We use a six-step framework that helps you move from vague problem statements to concrete designs you can explain confidently in interviews: Use the framework as a checklist during interviews: ask clarifying questions first, then estimate to show you can reason numerically, define APIs so your design has a contract, draw a high-level system diagram, deep dive into the most important components, and finish by discussing bottlenecks and mitigations.

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Common interview systems covered

  • URL Shortener
  • Rate Limiter
  • Notifications Service
  • News Feed / Timeline

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Hands-on Labs

You will complete four practical labs that reinforce the course concepts and give you implementation experience with typical interview building blocks:
  1. Implementing a basic URL shortener service (API, data model, storage).
  2. Building a distributed rate limiter (token bucket, counters, and storage).
  3. Designing a notification delivery pipeline (push vs pull strategies).
  4. Creating a simplified news feed pipeline (fan-out vs fan-in approaches).
These labs let you move beyond diagrams and actually implement the core logic and APIs often discussed in interviews.
A dark-themed infographic titled "System Design — Interview Prep" that shows a six-step framework with colored numbered blocks labeled Clarify, Estimate, API, High-Level Design, Deep Dives, and Bottlenecks. Below the steps are example systems like URL Shortener, Rate Limiter, Notifications, and News Feed.
Study tips: Practice the six-step framework aloud. Use a whiteboard (or a digital notepad) to sketch high-level diagrams quickly. Timebox each framework step in mock interviews to simulate real constraints.
Interview warning: Interviewers expect trade-off rationale. When you choose a component (e.g., SQL vs NoSQL, cache eviction policy), explain why that choice fits the constraints you established during Clarify and Estimate.

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How to use this lesson

  • Start by learning the framework; then apply it to one sample problem end-to-end.
  • Complete a lab after each topic to reinforce concepts.
  • In mock interviews, narrate your thought process and explicitly follow the framework steps.
Good luck — practice consistently, and use the six-step framework to structure clear, confident system design answers.

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