Design a Rate-Limited Public API

Each one worked end to end: requirements, estimates, the first diagram, the bottleneck that appears at scale, and the two or three deep dives an interviewer will push you into.

This module is 07.4 of the 6 in Design Case Studies. It runs about 3 hours across 5 lessons, and closes with Tenant — One customer is sending 90% of the traffic. Keep the other 4,000 inside their SLO.