“My assumption is this technology will eventually displace a lot of people in those warehouses,” Mr. Ford said. “I would not say that overnight huge numbers of jobs disappear. Maybe the first indication is they don’t get rid of those people but the pace of job creation slows down.”

Amazon’s Mr. Clark said history showed that automation increases productivity and, in some cases, demand from consumers, which ultimately creates more jobs. He said warehouse workers would continue to work in technologically rich environments.

“It’s a myth that automation destroys net job growth,” he said.

In the case of the Florence facility, it opened up the new opportunity for Ms. Scott.

At one point, one of the arms knocked over a tote, sending a dozen or so cone-shaped plastic coffee filters skidding across the ground. Ms. Scott hit a button that froze the arm so she could safely pick up the mess.

Then the arms started working again.

“The robot will work the same all day long,” said Edward Cohoon, who supervises Ms. Scott and other Amazon workers as they tend to individual robots. “Their stomachs don’t grumble.”