01
Level 1 of 5
Foundation
Read-heavy systems, short code generation, sharding fundamentals. Start here.
FOUNDATION
Unique ID Generator
Design a distributed ID generation service — globally unique, sortable, 10k IDs/sec. Covers UUID, Snowflake, ticket servers, and clock skew.
Snowflake UUID Ticket Server Clock Skew Fault Isolation
Open case study →
FOUNDATION
URL Shortener
Design bit.ly — takes a long URL, returns a short code, redirects at scale. 100M DAU, 1B redirects/day.
Sharding Hot Keys Caching Pre-Generated Keys Cold Storage Fault Isolation
Open case study →