Amazon is laying off another 9,000 workers, according to a memo to employees CEO Andy Jassy sent to workers on Monday. The employees affected by the cut include those in roles in AWS, Twitch, advertising, and human resources.

In his memo, Jassy cites the “uncertain economy” as the reason for the cuts and says the company has “chosen to be more streamlined in our costs and headcount.” Amazon just got done laying off a total of 18,000 people across the company late last year and in January, which included workers in its hardware and services, human resources, and retail teams.

“The overriding tenet of our annual planning this year was to be leaner while doing so in a way that enables us to still invest robustly in the key long-term customer experiences that we believe can meaningfully improve customers’ lives and Amazon as a whole,” Jassy writes in the memo.

Jassy also explains that the company didn’t announce all of the layoffs at the same time because some teams didn’t complete their internal analyses simultaneously.