Question: Design the system behind Amazon's warehouse fulfillment. This is uniquely Amazon.
Requirements: Inventory tracking across warehouses, order routing to nearest warehouse, pick/pack/ship optimization, out-of-stock handling.
Architecture: Inventory Service (real-time stock per warehouse), Order Router (selects warehouse by proximity, stock, cost), Task Assignment (pick tasks to workers), Shipping Integration (carrier APIs).
Scale: Millions of SKUs across hundreds of warehouses. Inventory updates must be near-real-time to prevent overselling. Event-driven: order triggers reservation, pick, pack, ship.
Discuss eventual consistency for inventory reads vs strong consistency for reservations.