System design interview problems

27 topics.

• 01FoundationReadDesign a URL shortenerShort codes and fast redirects at read-heavy scale.
• 02FoundationReadDesign PastebinText storage with expiry, split between metadata and blobs.
• 03FoundationReadDesign a distributed rate limiterAccurate limits across many servers without a bottleneck.
• 04SeniorReadDesign a key-value storePartitioning, replication, quorums and conflict resolution.
• 05FoundationReadDesign a unique ID generatorSortable 64 bit IDs at millions per second.
• 06Mid-levelReadDesign a web crawlerPoliteness, deduplication and a frontier for billions of pages.
• 07FoundationReadDesign a notification systemFan-out to push, SMS and email with retries and user preferences.
• 08Mid-levelReadDesign a news feedFan-out on write vs read, and the celebrity problem.
• 09Mid-levelReadDesign a chat systemPersistent connections, message ordering, and delivery receipts.
• 10Mid-levelReadDesign search autocompleteTop-k suggestions per prefix in under 100 ms.
• 11Mid-levelReadDesign InstagramPhoto uploads, storage tiers, and a feed for a billion users.
• 12SeniorReadDesign a video streaming serviceTranscoding pipelines, adaptive bitrate, and CDN economics.
• 13SeniorReadDesign DropboxChunked uploads, deduplication, and sync conflicts across devices.
• 14Mid-levelReadDesign a proximity serviceGeohashes and quadtrees for "what is near me".
• 15SeniorReadDesign a ride hailing serviceLive driver locations, matching, and surge at city scale.
• 16Mid-levelReadDesign a ticket booking systemSeat holds under a flash crowd without overselling.
• 17Mid-levelReadDesign a hotel reservation systemInventory, overbooking rules and idempotent bookings.
• 18SeniorReadDesign a payment systemIdempotency, double-entry ledgers and reconciliation.
• 19Mid-levelReadDesign a distributed cacheSharding, eviction, replication and hot keys.
• 20SeniorReadDesign a distributed message queuePartitioned logs, consumer groups and delivery guarantees.
• 21FoundationReadDesign a real-time leaderboardRanking millions of players with sorted sets and sharding.
• 22SeniorReadDesign top-k heavy hittersTrending items over sliding windows with sketches.
• 23SeniorReadDesign an ad click aggregatorStream aggregation with exactly-once counts and late events.
• 24SeniorReadDesign a metrics and monitoring systemTime series ingestion, downsampling and alerting.
• 25SeniorReadDesign a distributed job schedulerRunning millions of scheduled jobs exactly when they are due.
• 26SeniorReadDesign a collaborative editorConcurrent edits with operational transforms or CRDTs.
• 27SeniorReadDesign a stock exchangeMicrosecond matching, sequencing and market data fan-out.

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