This is _exactly_ how Amazon works. It has a best guess at inventory at a given moment, but it's a snapshot in time that is sometimes wrong. The inventory is ve

This is _exactly_ how Amazon works. It has a best guess at inventory at a given moment, but it's a snapshot in time that is sometimes wrong. The inventory is verified. The money is taken out. The pieces are all decoupled and essentially offline. This isn't a lie, it's an optimization and works quite well. If any piece fails, the recovery is obvious and easy to deal with.