In the shadow of Amazon’s offices in downtown Seattle, people enter a tiny grocery store, take whatever they want, and then walk out. And nobody runs after them screaming. This is what it’s like to shop at Amazon Go, the online retail giant’s vision for the future of brick-and-mortar stores. There are no checkout clerks, or even checkout stands. Instead, a smartphone app, hundreds of regular and infrared cameras on the ceiling (black on black, so they blend in), computer-vision algorithms, and machine learning work together to figure out what you’re picking up and charge you for it on a credit card connected to your Amazon account.