Part 4 — Case Studies

Real systems, real constraints. Apply everything from Parts 1-3.

Prerequisites: Part 3 — Architecture & Patterns (all chapters)

Overview

Part 4 applies every concept from previous parts to real-world system designs. Each chapter follows both interview-style (requirements → estimation → design → deep dive) and production-style (monitoring, failure modes, cost) approaches.

By the end of Part 4, you'll be able to:

Design a URL shortener handling billions of redirects
Architect a social media feed with fan-out strategies
Build a real-time chat system with delivery guarantees
Design a video streaming platform with adaptive bitrate
Create a ride-sharing system with geospatial matching

Chapters

Chapter 18 — URL Shortener & Pastebin

Base62 encoding, consistent hashing, read-heavy optimization, analytics tracking. The #1 interview question.

Fan-out on write vs read, hybrid approach for celebrities, feed ranking, notification system.

Chapter 20 — Chat & Messaging System

WebSockets, message delivery guarantees, group chat fan-out, online presence, end-to-end encryption.

Chapter 21 — Video Streaming Platform

Upload pipeline, transcoding, adaptive bitrate (HLS/DASH), CDN distribution, recommendation system.

Geohash/quadtree, driver matching, surge pricing, real-time tracking, trip lifecycle.

Time Estimate

~8 hours of focused reading and practice.

Part 1: Fundamentals

Part 2: Building Blocks

Part 3: Architecture & Patterns