Inside the factory-like environment of a fast-food kitchen, sodas should be the easiest menu item to serve. At my restaurant, a pair of machines pours them automatically as soon as we enter them into the system. All an employee has to do is snap a lid over the cup rim and lay a straw in the bag.

But the customers at the suburban California McDonald’s I’ve been working at for about a week don’t know that large meals come with medium drinks. In the space of a single shift, I twice make the error of putting the order in unaltered when a customer had really wanted a large drink to go with their large meal. Customers are understandably confused. I’m not allowed to be.

“You did it again!” Tranh, the store manager, shouts with the pickup window still open and the customer within earshot. “We don’t have time!”