// system design

System Design
Interview Prep

End-to-end breakdowns of real interview questions. From requirements to architecture to tradeoffs.

Free tools and study routes

Turn reading into estimates, failure timelines and practice.

Capacity calculatorEstimate QPS, bandwidth and storage. Share your assumptions.Inventory and payment failuresReplay overselling, late payments and duplicate callbacks.30 system design questionsSix practice stages, with a self-review check for every question.
01
System Design Design a News Feed Fan-out-on-write vs read, the celebrity hot-key problem, hybrid fan-out, and timeline caching.
Hard Jun 28, 2026 ↗
02
System Design Design a Notification System Multi-channel push/SMS/email, fan-out, dedup, retries with a DLQ, and delivery guarantees.
Hard Jun 28, 2026 ↗
03
System Design Design a Web Crawler URL frontier with politeness queues, dedup via Bloom filters, robots.txt, and crawl traps.
Medium Jun 28, 2026 ↗
04
System Design Design a Rate Limiter Token bucket vs sliding window, distributed counters in Redis with atomic Lua, and 429s.
Medium Jun 28, 2026 ↗
05
System Design Design a RAG System at Scale Chunking, the vector index (ANN), hybrid retrieval, reranking, and grounded answers with citations.
Hard Jun 16, 2026 ↗
06
System Design Design ChatGPT — an AI Chat Assistant Streaming (SSE), the GPU inference layer, an LLM gateway, memory & RAG, and cost tradeoffs.
Hard Jun 16, 2026 ↗
07
System Design Design Ticketmaster Seat holds and locking to prevent oversell, the virtual waiting room, and consistency.
Hard Apr 15, 2023 ↗
08
System Design Design a Payment System Idempotency, the double-entry ledger, exactly-once, reconciliation, and sagas.
Hard Apr 14, 2023 ↗
09
System Design Design a Leaderboard Redis sorted sets for O(log n) rank, persistence, sharding, and approximate rank.
Medium Apr 13, 2023 ↗
10
System Design Design Nearby / Yelp (Proximity) Geospatial indexing with geohash and quadtrees, the boundary problem, and caching.
Medium Apr 12, 2023 ↗
11
System Design Design Search Autocomplete (Typeahead) Tries, precomputed top-k suggestions, ranking, and the offline data pipeline.
Medium Apr 11, 2023 ↗
12
System Design Design Pastebin Key generation, metadata vs blob storage, read-heavy caching, and expiration.
Medium Apr 10, 2023 ↗
13
System Design Design a Distributed Key-Value Store Consistent hashing, quorums, replication, vector clocks, and gossip — Dynamo-style.
Hard Apr 09, 2023 ↗
14
System Design Design Google Drive / Dropbox File chunking, content-addressed dedup, metadata vs block storage, sync, and conflict resolution.
Hard Apr 08, 2023 ↗
15
System Design Design a Hotel Booking App Inventory locking, double-booking prevention, search ranking, and payment flows.
Medium Apr 01, 2023 ↗
16
System Design Design a URL Shortener Hash collision handling, redirect latency, analytics tracking, and custom slugs.
Medium Apr 01, 2023 ↗
17
System Design Design a Ride-share App Geo-indexing, driver matching, surge pricing, and trip state machine design.
Hard Apr 01, 2023 ↗
18
System Design Design a Chat App WebSockets, message fan-out, presence indicators, and real-time delivery.
Medium Apr 01, 2023 ↗
19
System Design Design a Video Streaming Platform CDN strategy, encoding pipeline, chunked delivery, and millions of concurrent viewers.
Hard Apr 01, 2023 ↗
20
System Design Design a Map Web App Geo-indexing, tile rendering, routing algorithms, and location search at scale.
Hard Apr 01, 2023 ↗
21
System Design Design an E-commerce Platform Product catalog, cart, inventory, payment processing, and order management at scale.
Hard Mar 31, 2023 ↗