Book Summaries | System Design Interview (Part 1) - A Framework for System Design Interviews

January 21st, 2024

Chapter 3: A Framework for System Design Interviews

This summary will serve to further cement my learnings taken when reading the third chapter of System Design Interview - An Insider's Guide (Part 1), titled A Framework for System Design Interviews, and I hope will provide some learnings to you as well.

Overview

• System design interviews are often intimidating and ambiguous.
• They simulate real-life problem-solving in collaboration with an interviewer.
• Focus on demonstrating design skills, defending choices, and responding constructively to feedback.
• Usually, the interviewer looks for collaboration, the ability to work under pressure, and asking good questions.
• Red flags include over-engineering, narrow-mindedness, and stubbornness.

A 4-step process for effective system design interview

1. Understand the problem and establish the design scope:

   • Slow down, think deeply, and ask questions to clarify requirements.
   • Avoid providing quick answers without thorough understanding.
   • Important to ask the right questions and make proper assumptions.
   • Document assumptions on the whiteboard or paper if required.
   • Questions may include specific features, user count, scaling expectations, and technology stack.

2. Propose high-level design and get buy-in:

   • Develop an initial blueprint, collaborate with the interviewer, and seek feedback.
   • Use box diagrams to illustrate key components like clients, APIs, servers, data stores, cache, CDN, etc.
   • Conduct back-of-the-envelope calculations to evaluate design against scale constraints.
   • Think out loud and communicate effectively during the design process.
   • Discuss concrete use cases to frame the high-level design.

3. Design deep dive:

   • Identify and prioritize components based on feedback and objectives.
   • Be aware that each interview is unique, and the focus may vary.
   • Manage time effectively, avoiding unnecessary details.
   • Dive into details of specific system components based on the interviewer’s cues.
   • Use concrete use cases to guide the detailed design process.

4. Wrap up:

   • Address follow-up questions and discuss potential improvements.
   • Recap the design to refresh the interviewer’s memory.
   • Discuss error cases, operational issues, and handling future scale curves.
   • Propose refinements if given more time.
   • Emphasize the importance of continuous communication and feedback.

Dos and Don’ts

Dos:

• Always ask for clarification and understand problem requirements.
• Communicate thoughts with the interviewer and suggest multiple approaches.
• Design critical components first after agreeing on the blueprint.
• Bounce ideas off the interviewer, treating them as a teammate.
• Keep persisting and seek feedback early and often.

Don’ts:

• Don’t jump into a solution without clarifying requirements and assumptions.
• Avoid excessive detail on a single component initially; provide a high-level design first.
• Don’t hesitate to ask for hints if you get stuck.
• Communicate actively and don’t assume the interview is done until feedback is received.
• Manage time effectively; system design interviews have broad scopes.

Time allocation on each step

• System design interviews have broad scopes and limited time (45 minutes to an hour).
• Rough guide for time distribution:
  • Step 1 (Understand the problem): 3 - 10 minutes.
  • Step 2 (Propose high-level design): 10 - 15 minutes.
  • Step 3 (Design deep dive): 10 - 25 minutes.
  • Step 4 (Wrap up): 3 - 5 minutes.