Flash-Sale Inventory Race Condition

Mobile e-commerce checkout is a textbook concurrency problem: many devices read the same stock count, wait through a network-plus-database round trip, then write a decision. This simulator renders that race in 3D — a central inventory silo drains as glowing request tokens fly in from every direction, resolving green (sold) or red (rejected) depending on the concurrency-control strategy you pick. Switch between no locking, optimistic concurrency (compare-and-swap on a version number) and pessimistic locking (a strict FIFO queue) while tuning starting stock, checkout rate and round-trip latency, and watch live readouts for stock remaining, units oversold, rejection rate, throughput and queue depth.