System Design AI

Guided practice

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

Classic designs 1

Ordered by design number

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

Live commentsClear filters

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

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