It’s Amazon’s fifth annual Prime Day. Or days? It’s 48 hours this time. Customers are expected to spend more than $5 billion, which means millions of orders processed in giant warehouses, which Amazon calls fulfillment centers. This work is increasingly automated, but there are more than 100,000 human workers in its North American centers because humans are more economical for some things, especially if they must work unceasingly. (7/16/2019)