The hype about Amazon and Whole Foods ignores the real logistical challenge of the grocery business at scale. Catching up with Walmart means delivering fresh food everywhere 24 hours a day, not just "in select markets during business hours." I'd put it this way, Walmart's infrastructure can move upscale in the grocery market more easily than Amazon/WF's infrastructure can scale up for grocery sales. A significant amount of Amazon's existing inventory sits as stock in a warehouse. Amazon is not nearly as driven by just in time contracts with suppliers as Walmart.