System Design Interview Labs

Architecture rounds,
made repeatable.

21 real case studies — URL shorteners to LLM inference serving — each with interviewer dialogue, an architecture blueprint, and a flow diagram you can narrate out loud.

Browse all case studies

Case studies

Your Interview Readiness Checklist

Unlocked case studies: 21

URL Shortener

Design a highly scalable service like Bitly to shorten long URLs into manageable links.

Open

Ride-Hailing Service

Architect a real-time platform like Uber to connect riders with drivers and manage trips.

Open

Video Streaming Platform

Design a massive-scale system like YouTube for video uploading, processing, and streaming.

Open

Free access

100%

of case studies open without membership

Playbook Section

Introduction

Understand expectations before touching diagrams.

21 of 21 case studies free

Review the FAANG evaluation rubric, pacing, and storytelling patterns. The interviewer wants clarity, not perfection.

Key Actions

▹Rehearse your opening 60 seconds (scope, clarifying questions, success metric).
▹Know the evaluation axes: requirements, API contracts, data model, scale math, resiliency.
▹Practice narrating trade-offs out loud with a timer.

Suggested Resources

▹Read the interview primer
▹Collect favorite prompts
▹Define your failure stories

The method

Your 45-minute system design framework

You don't need 15 memorized architectures — you need one repeatable way to attack a problem you've never seen. Every case study on this site follows these ten steps, so the pattern transfers to whatever your interviewer asks tomorrow.

Clarify

What are we building? Restate the problem in one sentence.

Scope

What are we NOT building? Cut features out loud.

Estimate

Users → QPS → storage → bandwidth. Let one number drive the design.

Model

Entities and API contracts before any boxes.

Architect

Draw the simplest system that satisfies the requirements.

Deep dive

Pick the 2–3 hardest problems and go deep only there.

Scale

Find the bottleneck. Fix that one, not everything.

Failure

What happens when each component breaks? Blast radius and recovery.

Trade-offs

Explain why this design — and what you gave up for it.

Summarize

Walk the interviewer through the final design end to end.

Learning journey

From first case study to staff-level architecture

Follow the stages in order. Each stage assumes the muscles built by the one before it.

Progression, not memorization

How every architecture grows

Never open with the final diagram. Start simple and let each new component earn its place — interviewers score the reasoning between levels, not the boxes.

Level 1 — Simple

Client → API → DB

Correct for thousands of users. Start here out loud — it proves you scale on evidence, not habit.

Level 2 — Production

Client
  ↓
Load Balancer
  ↓
API (n instances)
  ↓
Cache → DB

The LB exists for deploys and instance failure; the cache exists because reads dominate. Each box has a stated reason.

Level 3 — Scale

Client
  ↓
CDN / LB
  ↓
Services (split by domain)
  ↓
Cache tier
  ↓
Partitioned DB

Partitioning appears only when one primary provably cannot hold the write volume. Services split along team and failure boundaries.

Level 4 — Global

Users
  ↓
Global routing (GeoDNS/Anycast)
  ↓
Regional services
  ↓
Regional caches
  ↓
Replicated data

Regions exist for latency and jurisdiction, not vanity. Now consistency between regions is your hardest problem — say so.

Case Study Library

21 of 21 case studies

Case Study

URL Shortener

Beginner

Design a highly scalable service like Bitly to shorten long URLs into manageable links.

🎬 Video walkthrough · Hello Interview

Client

Edge POP

Redis

Architecture rounds,made repeatable.

Your Interview Readiness Checklist

Introduction

Your 45-minute system design framework

From first case study to staff-level architecture

Beginner

Core distributed systems

Real-time systems

Large-scale systems

AI infrastructure

Staff-level architecture

How every architecture grows

Case Study Library

URL Shortener

Ride-Hailing Service

Video Streaming Platform

Mobile OS Update

Music Streaming Platform

Microblogging Platform

LLM Serving (OpenAI/Gemini)

AI Pair Programming

Professional Network

Code Hosting Platform

Video Streaming (Netflix)

Google Borg

Multi-Agent AI Orchestration

RAG Pipeline at Scale

LLM Inference Serving at Scale

WhatsApp

Ticketmaster

Dropbox

Rate Limiter

Web Crawler

Google Docs

Video walkthroughs

Newly Released Content

Architecture rounds,
made repeatable.