Loop

Core Design Questions

The seven most-asked mid-level questions, each a step-gated framework walkthrough.

0 of 8 lessons complete · 191 min total

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  1. Walkthrough: Distributed Rate LimiterToken bucket vs sliding window algorithms, Redis-backed counters, and fail-open vs fail-closed decisions.Walkthrough · 25 minNot completed
  2. Walkthrough: News FeedFan-out on write vs read, the celebrity problem, feed ranking, and cache-heavy timeline reads.Walkthrough · 25 minNot completed
  3. Walkthrough: Chat SystemWebSocket connection management, message ordering and delivery guarantees, presence, and group-chat fan-out.Walkthrough · 25 minNot completed
  4. Walkthrough: Video PlatformChunked uploads to blob storage, an encoding pipeline on queues, CDN delivery, and adaptive bitrate streaming.Walkthrough · 25 minNot completed
  5. Walkthrough: Ride SharingProximity search with geohashing/quadtrees, high-frequency location updates, and the matching flow.Walkthrough · 28 minNot completed
  6. Walkthrough: Ticket BookingInventory contention, seat locking with TTLs, idempotent payments, and handling flash-sale spikes.Walkthrough · 28 minNot completed
  7. Walkthrough: Notification SystemMulti-channel push/email/SMS delivery, provider abstraction, retries with dedupe, and user preference routing.Walkthrough · 25 minNot completed
  8. Core Questions CheckpointCross-question pattern recognition: which storage, queue, and caching choices recur and why.Checkpoint · 10 minNot completed