Amazon Go is live in San Francisco.

The first San Francisco location of the cashier-less convenience store concept opened today at 300 California St. The 2,300-square-foot store is the sixth to open so far, following three locations in Amazon’s hometown of Seattle and two in Chicago.

Amazon announced a second store in San Francisco at 98 Post St. that will open this winter. Amazon previously announced a future third store in Chicago, and added to that expansion today with a fourth location coming next year to the Illinois Center development south of the Chicago River.

That makes nine Amazon Go stores either opened or announced by Amazon, and the company also confirmed a future location in New York City.

These new locations follow up on a plan first disclosed by Amazon earlier this year to open Go stores outside of Seattle, with Chicago and San Francisco named as the first expansion markets.

After spending years developing the technology behind the store, and another year testing it with Amazon employees, the tech giant is speeding up the pace of Amazon Go expansion. In late September reports surfaced that Amazon is considering opening up to 3,000 Amazon Go locations by 2021.

Started in January as a corporate in-house project looks to change the way stores will run forever.

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.

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.

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, items from local producers and some grocery essentials.

In addition to the expansion of Amazon Go, the company recently debuted a new retail concept in New York City. Amazon 4-star features the highest rated items online, as well as new or trending items.