Amazon today debuted the third location of its checkout-less grocery concept Amazon Go, the second store opening in a week.

The new location is in one of Amazon’s office buildings at 300 Boren Ave. N. in the South Lake Union neighborhood. It is the biggest of the three stores — 2,100 square feet versus 1,800 for the original store and 1,450 square feet for the second location.

After spending years developing the technology behind the store, and another year testing it with Amazon employees, the tech giant is starting to move faster in expanding Amazon Go. The original store opened in January in the base of Amazon’s Day One officer tower. The second store at the Madison Centre office building in downtown Seattle opened just over a week ago. 

The expansion will continue, as Amazon plans to open stores in San Francisco and Chicago. Earlier this year, Recode reported that Amazon intends to open as many as six additional Amazon Go stores beyond the original Seattle location.

The store relies heavily on the Amazon Go smartphone app. Customers scan a unique QR code within the app before passing through a set of glass doors, similar to the gates Amazon employees go through when entering their office buildings every morning. A vast array of overhead cameras and weight sensors in the shelves automatically track what people pick up and take from the store.

Each store features a mix of grab-and-go breakfast, lunch and dinner options such as salads and sandwiches. Also prominent in Amazon Go stores are Amazon Meal Kits and some grocery essentials.

When customers leave, they just walk out. Amazon Go’s systems automatically debit their accounts for the items they take, sending the receipt to the app. By logging shoppers in at the entrance, then tracking their actions in the store, the system eliminates the need for traditional checkout registers and checkout workers along with them.

Amazon Go drew giant lines when it opened in Seattle earlier this year. The store has a 4.5-star rating on Yelp, with customers raving about the concept. The opening day of store No. 2 didn’t draw the same fanfare, though it did attract a steady stream of customers.

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