System Design AI

Guided practice

Start with a template. Work through each step. Ask Coach when you need a second opinion.

Classic designs 3

Ordered by design number

Company tags are community-reported. Counts on cards show how many people reported that design.

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49. Design an Online Auction like eBay
Take bids on 10 million live auctions with one consistent highest bid, lose none, push the price to every watcher and end each auction fairly.
ClassicMedium
Streaming Concurrency Distributed systems
+7
Auctions Aurora AWS Contention Kafka Real time Server sent events
Worked design
Practice
60. Design Live Comments like Facebook Live
Live comments for millions of viewers: SSE streams, a Redis channel per video with co-located viewers, sampling and CDN snapshots for hot videos.
ClassicMedium
Databases AWS DynamoDB
+5
Fan out Live comments Real time Redis Pub/Sub Server sent events
Worked design
Practice
63. Design Real-Time Updates for Millions of Clients
Every goal on 25 million open apps within two seconds: SSE or WebSockets, pub/sub to the right server, resume by seq, hot topics, reconnect storms and push.
ClassicMedium
Queues AWS Publish / subscribe
+4
Push notifications Real time Server sent events WebSockets
Worked design
Practice

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