System Design·60 minMembers

Subreddit Live Chat System

Members only

Design Reddit's subreddit live-chat product (real-time chat anchored to a subreddit, room sizes ranging from tens to millions during live events). The Super Bowl scenario — fan-out to ~5M concurrent u...

SWE

chat

websocket

fan-out

messaging

presence

scaling

medium

Frequency

Low

Last asked

2026-04-12

Stage

onsite-system-design

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