You detect this when you load something into your cart, then abandon the cart because you realize you can’t afford it or get distracted somehow, and a day or two later it shows up anyway.
Their distribution system is amazing, and it just keeps growing. A couple of years ago, most of my stuff would come from Seattle or somewhere on the east coast, now it usually comes from a fulfillment facility that’s about a hundred miles away. Through a combination of Fedex driving the order to the local post office, and my letter carrier bringing it, I often get the order in less than 24 hours.
What they’re proposing to do is keep track of your usual orders, make sure they’re at the closest facility, and preposition them if they’re not. With the new “locker” program, you’ll be able to order stuff at bed time, and swing by the local convenience store to pick it up the next morning. Bezos is one clever guy.
It can also be inferred if the user routinely orders the same product over time such as paper products, etc. However, I bet the user needs to opt-in or opt-out of this program.