| 1 | Bitly | Foundation problem | API, DB, ID generation, caching, read-heavy scaling |
| 2 | Rate Limiter ⭐ | Very reusable infra question; also appears on HelloInterview’s Microsoft guide | Redis, token bucket/sliding window, distributed state, atomicity |
| 3 | WhatsApp ⭐ | Real-time systems | WebSockets, presence, message delivery, queues, offline users |
| 4 | Ticketmaster ⭐ | Excellent concurrency question | overselling, locking, transactions, reservation/hold, queues |
| 5 | FB News Feed ⭐ | Classic scaling problem | fan-out, push vs pull, caching, feeds, celebrity problem |
| 6 | Dropbox | Storage architecture | blob/object storage, metadata, chunking, uploads, sync |
| 7 | Distributed Cache ⭐ | Strong infrastructure fundamentals | consistent hashing, replication, eviction, failures |
| 8 | Yelp | Search + geo | geospatial indexing, search, pagination, read-heavy design |
| 9 | LeetCode | Async execution architecture | job queues, workers, sandbox/execution, result storage |
| 10 | Instagram | Combines many patterns | media storage, CDN, feeds, metadata, scaling |