Case Studies
Full interview case studies: framing, fault lines, failure modes, rubrics, drills and incident deep dives, from L5 through L7.
Core Ten
Ten problems that show up in almost every Staff loop, either as the whole prompt or as the hard part of a bigger one. Master these first.
- Rate LimitingDesign a Distributed Rate Limiter91 min · 10 diagrams
- Distributed CachingDesign a Distributed Cache88 min · 11 diagrams
- Message QueuesDesign a Distributed Message Queue89 min · 7 diagrams
- Circuit BreakersDesign for Fault Tolerance82 min · 9 diagrams
- Service DiscoveryDesign Service Discovery69 min · 6 diagrams
- ID GenerationDesign a Distributed ID Generator83 min · 7 diagrams
- Idempotency & Exactly-OnceDesign Idempotent APIs81 min · 9 diagrams
- Distributed Lock ServiceDesign a Distributed Lock Service82 min · 8 diagrams
- Multi-Region Active-ActiveDesign for Multi-Region Active-Active79 min · 8 diagrams
- Ad Click AggregatorDesign a Real-Time Ad Click Aggregator80 min · 7 diagrams
Latency-Sensitive
Every millisecond is someone's budget. Who spends it?
Data-Heavy
Volume changes the shape of every decision.
Correctness-Critical
Where a lost update is a lawsuit, not a blip.
Product Case Studies
The classic "Design X" prompts, taught through the Staff and Principal lens.
- Distributed Job SchedulerDesign a Distributed Job Scheduler73 min · 6 diagrams
- LeaderboardDesign a Leaderboard63 min · 6 diagrams
- Notification SystemDesign a Notification System60 min · 6 diagrams
- Replicated Data StoreDesign a Replicated Data Store73 min · 8 diagrams
- Stock ExchangeDesign a Stock Exchange66 min · 7 diagrams
- URL ShortenerDesign a URL Shortener66 min · 7 diagrams
- Web CrawlerDesign a Web Crawler73 min · 8 diagrams
- Blob StorageDesign Blob Storage (S3)71 min · 7 diagrams
- Metrics & MonitoringDesign Datadog66 min · 7 diagrams
- File SyncDesign Dropbox78 min · 6 diagrams
- Auto-Scaling & CapacityDesign for Auto-Scaling71 min · 8 diagrams
- Database SelectionDesign for Database Selection73 min · 8 diagrams
- Collaborative EditingDesign Google Docs70 min · 7 diagrams
- Maps & GeospatialDesign Google Maps62 min · 7 diagrams
- News FeedDesign Instagram Feed56 min · 6 diagrams
- Code ExecutionDesign LeetCode70 min · 8 diagrams
- Real-Time UpdatesDesign Real-Time Updates (WebSockets)65 min · 7 diagrams
- Flash Sales & TicketingDesign Ticketmaster61 min · 7 diagrams
- Proximity MatchingDesign Tinder75 min · 7 diagrams
- Ride Hailing & DeliveryDesign Uber66 min · 7 diagrams
- Chat MessagingDesign WhatsApp64 min · 6 diagrams
- Search TypeaheadDesign Search Autocomplete74 min · 8 diagrams