System designHardsd-g519

Subject Live commentsLevel Mid–Staff~45 minCommon in Networking & APIs · Distributed systems interviewsIndustries Technology, Software development

Question

Design the live-comments/chat system for a massive livestream. A single stream can have 2M concurrent viewers; at peak (a goal, a product reveal) tens of thousands of comments per second are posted, and every viewer wants a live-feeling comment feed. You obviously can't show all comments to everyone, and you must handle spam, slow-mode, and moderation in real time.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.