Designs

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Designs with worked examples 8

Ordered by design number

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4. Design a Notification System
Deliver email, push and SMS with preferences, retries and honest delivery status.
ClassicMedium
Queues Streaming Distributed systems
+10
AWS Delivery semantics Fan out Kafka Notifications Real time Reliability Retries Amazon SQS User preferences
Worked design
Practice
35. WebSocket Gateway and Session Registry
To push a message to someone you must find the one server out of hundreds that currently holds their connection — and connections are long-lived, unevenly distributed, and disappear without warning.
Product & backendMedium
Chat Presence Real time
+1
WebSockets
Worked design
Practice
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
53. Design a Stock Trading App like Robinhood
Live prices to five million phones through per-symbol pub/sub, and market and limit orders over FIX that are never lost, sent twice or overspent.
ClassicMedium
Queues AWS FIX protocol
+5
Publish / subscribe Real time Reconciliation Trading WebSockets
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
61. Design a Collaborative Editor like Google Docs
A hundred people typing in one document, every copy converging, nothing acknowledged lost: one owner per document, an op log with snapshots, and fenced failover.
ClassicMedium
Databases Distributed systems AWS
+6
Collaboration Consistent hashing DynamoDB Operational transform Real time WebSockets
Worked design
Practice
95. Design a Team Chat App like Slack
Design a team chat app like Slack: channels and DMs in real time, threads, unread counts and search. One-hour boards for junior, senior and staff, with the theory behind them.
ClassicMedium
Databases Search AWS
+5
DynamoDB Fan out Messaging Real time WebSockets
Worked design
Practice
96. Design a Food Delivery App like Uber Eats
Find restaurants that deliver to you, check out without double charges, time couriers to the kitchen and track them live.
ClassicMedium
AWS Booking Dispatch
+3
Geospatial Payments Real time
Worked design
Practice

Each design brings together the brief, practice, examples and discussion.

Designs with worked examples 8

4. Design a Notification System

35. WebSocket Gateway and Session Registry

49. Design an Online Auction like eBay

53. Design a Stock Trading App like Robinhood

60. Design Live Comments like Facebook Live

61. Design a Collaborative Editor like Google Docs

95. Design a Team Chat App like Slack

96. Design a Food Delivery App like Uber Eats