Your comment intrigued me, so I found this article: https://www.recode.net/2018/1/21/16913984/what-does-photos-amazon-jeff-bezos-seattle-new-no-cashier-line-gr

Your comment intrigued me, so I found this article: https://www.recode.net/2018/1/21/16913984/what-does-photos-amazon-jeff-bezos-seattle-new-no-cashier-line-grocery-story-amazon-go https://www.recode.net/2018/1/21/16913984/what-does-photos-a... I don't think there can be any floor sensors there. There may be inventory-counting shelf sensors, I have no idea. There definitely isn't RFID. Looks like massive camera arrays in the ceiling.