SYSTEM DESIGN INTERVIEW PREP

Master System Design.
One Case Study at a Time.

Notes I built while prepping. Rough around the edges, but honest.

LEARNING PATH

LV 1

Foundation

The classics. Every interview starts here. Get these cold before moving up.

1 case study

Foundation

URL Shortener

Design bit.ly. The classic starter — every foundational concept lives here.

Short Code GenDB ShardingCachingHot KeysCold StorageFault Isolation

LV 2

Ascent

Mid-level systems. Real trade-offs, multiple moving parts.

1 case study

Ascent

Pastebin

Design pastebin.com. Deceptively deep — content addressing, async uploads, distributed cleanup.

Content AddressingRef CountingAsync UploadsExpiry JobsCircuit BreakerFault Isolation

LV 3

Expedition Coming Soon

Senior-level systems. Distributed complexity, scaling decisions under pressure.

0 case studies

LV 4

Summit Coming Soon

Advanced distributed systems. This is principal-level territory.

0 case studies

LV 5

Battleground

Elite-level systems. Many failure modes, no easy answers. This is where interviews are won or lost.

1 case study

Battleground

WhatsApp

500M DAU real-time messaging. WebSockets, ordering, offline delivery, read receipts, thundering herd.

WebSocketsMsg OrderingOffline DeliveryRead ReceiptsInboxThundering HerdRate Limiting