Bloomberg/Getty Images Walmart's online business is booming, with the bulk of sales fulfilled through local stores. The job of picking items for these orders falls to store workers who may pull hundreds of items per shift. When a relatively small picking rule change caused a big stir, it highlighted the tension for teams. Walmart has a need for speed. The retail giant has been growing its online business for years, fueled in large part by its ability to get groceries to customers in nearly eve