System designHardsd-g277

Subject Pub subLevel Senior–Staff~50 minCommon in Databases & SQL · Distributed systems interviewsIndustries Technology, Software development

Question

Design a live-auction / real-time bidding system for high-demand drops (limited sneakers, concert tickets, NFT mints) where up to 1M users watch one auction and tens of thousands bid in the final seconds. Every watcher must see the current high bid update near-instantly; bids must be accepted in a fair, well-defined order; and exactly one winner must be declared with no double-sell. The closing seconds are a thundering herd. How do you accept bids consistently and fan out the current price to a million watchers under that spike?

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.