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System Design Interview Guide

Your comprehensive resource for mastering system design interviews — 75+ topics across software engineering, ML, and GenAI, with step-by-step walkthroughs, architecture diagrams, code examples, and interview transcripts.

Who Is This For?

You Are Start Here You'll Learn
Staff / L6 Engineer targeting Google, Meta Staff Engineer Track Multi-region architecture, SLOs, consensus, leadership signals
Senior SDE preparing for FAANG Fundamentals → System Design Core system design patterns and trade-offs
ML/AI Engineer designing production systems GenAI/ML Fundamentals → ML Design ML-specific architectures and serving patterns
GenAI Engineer building LLM-powered products GenAI/ML Fundamentals → GenAI Design LLM serving, RAG, agents, safety at scale
Student / Junior Dev wanting to level up Fundamentals Foundational concepts with clear explanations

Tip

Follow these paths in order. Each builds on the previous. Skip sections you're already confident in.

Path 1: Software System Design (SDE / Senior SDE)

Week 1-2: Fundamentals
  Interview Framework → Estimation → Networking → Databases → Caching → Load Balancing

Week 3-4: Core Design Problems
  URL Shortener → Rate Limiter → Key-Value Store → Distributed Cache → Chat System

Week 5-6: Complex Systems
  News Feed → Video Streaming → Collaborative Editor → Payment System → Message Queue

Week 7-8: Advanced Topics + Practice
  Consensus → Distributed Transactions → Sharding → Event Sourcing → Mock interviews

Path 2: ML System Design (ML Engineer)

Week 1-2: Software Fundamentals (abbreviated)
  Databases → Caching → Distributed Systems → Message Queues

Week 3-4: ML Fundamentals
  Model Serving → Feature Stores → Data Pipelines → Distributed Training → LLM Evaluation → RLHF & Alignment

Week 5-6: ML Design Problems
  Recommendation System → Fraud Detection → Search Ranking → Ads Ranking → Machine Translation

Week 7-8: Practice
  Image Search → Real-time Personalization → Speech Recognition → Feature Platform → Mock interviews

Path 3: GenAI System Design (GenAI / LLM Engineer)

Week 1-2: Foundations
  Distributed Systems → ML Fundamentals (Model Serving, Feature Stores)
  LLM Systems (RAG, fine-tuning, vector DBs) → Distributed Training → LLM Evaluation → RLHF & Alignment

Week 3-4: GenAI Design Problems
  LLM Chatbot → Enterprise RAG → Document Q&A → AI Code Assistant → LLM Gateway

Week 5-6: Advanced GenAI
  AI Agent System → Content Moderation → Hallucination Detection → Text-to-Image → Multi-Modal Search

Week 7-8: Infrastructure + LLM Ops + Practice
  ML Training Platform → Fine-Tuning Platform → LLM Evaluation Pipeline → Prompt Management
  Mock interviews with interview transcripts

Path 4: Staff Engineer (L6) — All Domains

Week 1-2: Master Fundamentals + Advanced
  All Basics → Consensus → Distributed Transactions → Sharding → Observability

Week 3-4: Priority Designs (deep)
  Key-Value Store → Rate Limiter → Collaborative Editor → Task Scheduler → Payment System

Week 5-6: ML/GenAI Depth
  LLM Chatbot → Enterprise RAG → ML Training Platform → Ads Ranking

Week 7-8: Leadership + Practice
  Staff Engineer Guide → Behavioral & Leadership → Read interview transcripts → Mock interviews

What's Inside

Fundamentals

Start here. The building blocks that appear in every system design interview.

Advanced Topics

Deep dives for Senior and Staff-level interviews.

Staff Engineer (L6) Interview Track

Targeting Google, Meta, or other top companies at the Staff / Principal / L6 level?

System Design Examples

Step-by-step walkthroughs of classic interview questions — 28 designs.

Infrastructure & Data:

Communication & Social:

Media & Content:

Real-time & Geo:

Commerce:

Data Infrastructure:

Search:

GenAI/ML Fundamentals

Core building blocks — master these before ML and GenAI design questions. 7 topics.

ML System Design

Production ML systems — 10 designs covering ranking, retrieval, personalization, NLP, and feature infrastructure.

GenAI System Design

Production GenAI systems — 15 designs with Google-style interview transcripts.

How to Use This Guide

If You Have 1 Week

  1. Read Interview Framework — know the 4-step approach
  2. Study URL Shortener and Rate Limiter
  3. For ML roles: add Recommendation System
  4. For GenAI roles: add LLM Chatbot — read the interview transcript
  5. Practice explaining designs out loud

If You Have 1 Month

Follow the Learning Path for your target role above.

During Your Interview

  1. Clarify requirements (5 min) — Don't assume!
  2. High-level design (10 min) — Draw the big picture
  3. Deep dive (15 min) — Focus on 2-3 components
  4. Wrap up (5 min) — Discuss trade-offs and improvements

Key Tips

Note

Always ask clarifying questions. The interviewer wants to see how you think, not just what you know.

Tip

Draw diagrams. A picture is worth a thousand words in system design.

Warning

Don't jump to solutions. Understand the problem before proposing architecture.

Content Overview

Section Topics Difficulty
Fundamentals 11 essential topics Beginner-Advanced
Advanced Topics 13 deep-dive topics (incl. L6 track) Advanced-Expert
System Design Examples 28 classic problems (incl. Staff Guide) Intermediate-Hard
GenAI/ML Fundamentals 7 ML/GenAI building blocks Medium-Hard
ML System Design 10 ML systems Hard
GenAI System Design 15 GenAI systems (with interview transcripts) Very Hard
Total 84

Contributing

Found an error? Want to add a new design? Contributions are welcome! Open an issue or submit a pull request on GitHub.

**Good luck with your interviews!** *Remember: The goal isn't to give a "perfect" answer. It's to demonstrate clear thinking and good engineering judgment.*