Hard

High-level design problems at SDE-3 / Staff level. Focus: multi-region, consensus, complex trade-offs, production operations.

Problems

Problem	File	Key concepts
Distributed Cache (Redis)	distributed-cache.md	Consistent hashing, replication, failover
Distributed Message Queue (Kafka)	distributed-message-queue.md	Partitioning, replication, consumer groups
Payment System	payment-system.md	ACID, idempotency, double-entry
Ride Sharing	ride-sharing.md	Real-time location, geospatial, matching
Google Drive	google-drive.md	Sync, conflict resolution, chunking
Chat System	chat-system.md	WebSockets, message queue, presence
Search System	search-system.md	Inverted index, ranking, scaling

Use the HLD template and SYSTEM_DESIGN_INTERVIEW_FRAMEWORK.md when practicing.