War Rooms
Eight guided design sessions. Each one builds a real system stage by stage — requirements, estimation, architecture, then the hard scaling questions.
From One Server to Planet Scale
w2The vocabulary lesson — every system design answer is built from these six moves.
URL Shortener
w3The 'hello world' of system design — every concept in miniature.
Design a Rate Limiter
w4Small surface, deep trade-offs — the classic 'do you actually understand distributed state?' question.
Design a News Feed
w5The fanout question — push vs pull, and the celebrity who breaks both.
Design a Notification System
w5The canonical queue question — decoupling, retries, and idempotency in one design.
Design a Chat System
w6WhatsApp-style messaging — the case that teaches you stateful servers.
Design Video Streaming (YouTube-lite)
w7Two systems in a trench coat — a write-heavy pipeline and a read-heavy edge, joined by a CDN.
Distributed Key-Value Store
w7Dynamo in five moves — the most conceptual case you'll ever be asked.