Amazon is cutting hundreds of jobs in its consumer business in Seattle, a person familiar with the matter said on Monday, as the company shifts resources into fast-growing areas like its work on voice assistant Alexa.

The job cuts, rare for the world’s largest online retailer, are in the low hundreds, the person said on condition of anonymity. Amazon determined through planning for 2018 that certain mature areas of its business no longer required as much staff for the results it was seeking, the person said.

It was unclear which specific teams inside Amazon were affected. Amazon’s consumer organization includes its retail and marketplace businesses, as well as programs like food delivery service Amazon Restaurants.

Seattle-based Amazon has been on a hiring tear, creating some 130,000 jobs worldwide in 2017 and announcing plans to open a second headquarters in North America, anticipating up to 50,000 more jobs there. Its full-time and part-time headcount surged 66 percent in the fourth quarter, to 566,000, from a year earlier. That figure includes employees at Whole Foods Market, which Amazon acquired in a $13.7 billion deal last year.

But many of the corporate jobs are going to areas of soaring profit, like cloud-computing division Amazon Web Services, or areas where Amazon sees potential, like voice-controlled computing.

“Our 2017 projections for Alexa were very optimistic, and we far exceeded them,” said Jeff Bezos, Amazon’s founder and chief executive, in a statement earlier this month. “We don’t see positive surprises of this magnitude very often — expect us to double down.”

Amazon hopes Alexa will become a regular part of consumers’ lives and will spur shopping orders by voice.

The company currently has 3,900 jobs open in Seattle, and staff facing job cuts can apply for them. The company has contracts for 1 million square feet or more of new office space in the city to hire still more employees.

The Seattle Times earlier reported the job cuts.