How Distributed Unit Rows Beat Hot Counters in Flash-Sale Systems

Flash sales reveal a hidden complexity in concurrency: a shared inventory counter becomes a bottleneck under optimistic concurrency control, triggering write collisions and retry storms that devastate throughput. By modeling each sellable unit as an independent database row that buyers randomly claim atomically, this approach eliminates contention while guaranteeing strong consistency across global regions—precisely what high-traffic flash sales demand.