Guided practice

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

• 

  5. Design a Chat System

  Send durable messages, reconnect devices and explain ordering and delivery receipts.

  ClassicMedium

  DatabasesSecurityPrivacy

  +11

  Distributed systemsAWSChatDynamoDBEnd to end encryptionMessagingMulti regionOffline firstOrderingRedis Pub/SubWebSockets

  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

  DatabasesAWSDynamoDB

  +5

  Fan outLive commentsReal timeRedis Pub/SubServer sent events

  Worked design

  Practice

Self-paced by default. Your answers and canvas stay private. AI feedback runs only when you ask for it.