Amazon confirmed last month that Amazon Go convenience stores are slated for Chicago and San Francisco, but no timetable was provided. The first Amazon Go, an 1,800 square foot store that carries mostly food and beverages along with some nonfood items like batteries and over-the-counter medicine, opened in Seattle in January.

Go stores feature checkout-free shopping made possible by the company’s “Just Walk Out” technology. Overhead cameras and weight sensors detect merchandise that shoppers take from and return to shelves, and keep track of items selected in a virtual cart.

Shoppers use the Go mobile app to gain entry, and when they leave the store, their Amazon account is automatically charged for the items they took with them.