System Design

0
System design questions
Learn

Fundamentals.

28 illustrated guides, about 5 hours end to end. Foundations first, then the building blocks, then full worked designs.

1Foundations

Read these first: how systems scale, how to estimate, and how to run the interview.

3 guides
  1. #1 8 min 11Scaling a web app from one server to millions of usersLoad balancers, replication, caching, CDNs, stateless tiers, queues and sharding: the building blocks every design reuses.Read
  2. #2 3 min 1Capacity estimation in your headPowers of two, latency numbers, availability nines and a worked QPS and storage estimate.Read
  3. #3 3 minThe system design interview playbookA four-step flow (scope, high-level design, deep dive, wrap-up), what to say, what to avoid, and how to split 45 minutes.Read

2Building blocks

Components that show up inside almost every design.

4 guides
  1. #4 4 min 8Rate limitingToken bucket, leaky bucket, fixed and sliding windows, and where the limiter lives.Read
  2. #5 5 min 10Consistent hashingWhy modulo hashing breaks, the hash ring, virtual nodes and which keys move when servers change.Read
  3. #6 11 min 17Distributed key-value storesPartitioning, replication, quorum consistency, vector clocks, hinted handoff, Merkle trees and the read/write paths.Read
  4. #7 3 min 5Unique IDs at scaleMulti-master increments, UUIDs, ticket servers and Snowflake-style 64-bit IDs.Read

3Worked designs

Full walkthroughs of classic interview systems, step by step.

21 guides
  1. #8 4 min 7URL shorteningHash-and-collision versus base-62 encoding, redirects, caching and the data flow.Read
  2. #9 5 min 4Web crawlingSeed URLs, the URL frontier, politeness, priority, dedup and traps.Read
  3. #10 4 min 6Notification deliveryPush, SMS and email providers, queues, retries, rate limits and user settings.Read
  4. #11 4 min 5News feedsFan-out on write versus on read, feed caches and the publish and retrieval flows.Read
  5. #12 7 min 14Chat and messagingWebSockets, message storage, message ids, group chat, presence and sync across devices.Read
  6. #13 6 min 9Search autocompleteTrie data structure, data gathering pipeline, sharding and caching the top suggestions.Read
  7. #14 7 min 14Video streaming platformUpload flow, transcoding DAGs, CDN delivery, adaptive streaming and cost control.Read
  8. #15 7 min 9Cloud file storage and syncBlock-level uploads, metadata database, sync conflicts, notifications and storage savings.Read
  9. #16 10 min 14Proximity searchGeohash, quadtrees and Google S2 for finding nearby businesses, plus caching and scaling.Read
  10. #17 11 min 10Live location sharingWebSocket servers, a location cache, pub/sub fan-out and scaling to millions of moving users.Read
  11. #18 15 min 22Maps and navigationMap tiles, geocoding, routing graphs, ETA and the location and navigation services.Read
  12. #19 25 min 34Distributed message queuesTopics, partitions, consumer groups, replication, delivery semantics and the broker's data layout.Read
  13. #20 18 min 22Metrics, monitoring and alertingTime-series storage, pull versus push collection, aggregation, query service and alerting.Read
  14. #21 22 min 29Click event aggregationStreaming aggregation, exactly-once concerns, watermarks, reconciliation and fault tolerance.Read
  15. #22 18 min 17Hotel reservationsInventory model, double-booking prevention, concurrency control and scaling the reservation service.Read
  16. #23 13 min 14Email at scaleSending and receiving flows, mail storage, search, deliverability and spam handling.Read
  17. #24 18 min 23Object storage internalsBuckets and objects, data versus metadata stores, replication, erasure coding and garbage collection.Read
  18. #25 16 min 23Real-time leaderboardsSorted sets, score updates, top-k and rank queries, and sharding by score range.Read
  19. #26 14 min 10PaymentsPay-in and pay-out flows, ledgers, idempotency, reconciliation and handling failures.Read
  20. #27 19 min 25Digital walletsBalance transfers, distributed transactions, event sourcing and reproducibility.Read
  21. #28 22 min 24Stock exchangeOrder matching, market data, low-latency design and fault tolerance.Read

Each worked design links back to the matching question in the question bank, and every question links here.

Search

Jump to any problem, company or topic