Amazon.com Inc (AMZN.O) 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.

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.