Prompts
Run these drills weekly.
Even 20 minutes of constraints + bottlenecks builds strong intuition.
Design a URL shortener
Capacity planning, storage, caching, and collision strategy.
Design a feed
Fan-out models, pagination, ranking, and hot key mitigation.
Design a chat system
WebSockets, delivery guarantees, offline sync, and sharding.
Design file storage
Object storage, metadata, consistency, and CDN strategy.
Mental checklist
- Clarify requirements and non-goals first.
- Estimate scale: QPS, storage, bandwidth, and hot paths.
- Choose data model + APIs. Then sketch components.
- Identify bottlenecks and failure modes.
- Iterate: caching, queues, replication, sharding, observability.