CNN Business  — 

Dave Clark, Amazon’s Worldwide Consumer CEO, is resigning after 23 years at the e-commerce giant.

Amazon (AMZN) announced Clark’s resignation, effective July 1, in a regulatory filing with the US Securities and Exchange Commission Friday. In a tweet, Clark said: “I’ve had an incredible time at Amazon (AMZN) but it’s time for me to build again. It’s what drives me.”

During his time at Amazon, Clark helped build and oversee the company’s sprawling logistics network of warehouses, delivery trucks, planes and cargo ships, which helped it expedite shipping times and dominate the online retail market.

His departure, however, comes as Amazon faces several new challenges, including slowing growth, mounting regulatory scrutiny and a growing number of organizing efforts among warehouse workers. In particular, the consumer segment has been under strain, while its AWS cloud services business continues to generate huge profits.

Amazon experienced a surge in demand and hiring during the pandemic as shoppers shifted more of their purchases online. But in April, Amazon reported slowing revenue growth and higher costs during the first quarter of the year, sending its share price down sharply.

Andy Jassy, who took over as CEO of Amazon last summer from founder Jeff Bezos, said in a statement with the most recent earnings report that “the pandemic and subsequent war in Ukraine have brought unusual growth and challenges.” Jassy also noted the company continues to “work through ongoing inflationary and supply chain pressures.”

In his note to Amazon staff on Friday, Clark alluded to some of those challenges and expressed confidence in the team to push past them.

“We have a great leadership team across the Consumer business that is ready to take on more as the company evolves past the customer experience challenges we took on during the Covid-19 pandemic,” he wrote. “We also have a solid multi-year plan to fight the inflationary challenges we are facing in 2022.”

Amazon has also faced multiple unionization efforts in recent months, including in Staten Island, New York, where workers at one warehouse voted to form the e-commerce giant’s first-ever US labor union in April. Amazon is appealing the results, calling for a do-over of the union election.

Clark has publicly defended the company amid the unionization efforts and scrutiny of its treatment of workers. He made headlines last year for taking a swipe at Bernie Sanders on Twitter after the senator hosted a rally in support of Amazon workers seeking to unionize at an Alabama facility.

“I often say we are the Bernie Sanders of employers, but that’s not quite right because we actually deliver a progressive workplace,” Clark said in a since-deleted tweet. The Amazon union election in Bessemer, Alabama, concluded earlier this year with the results too close to call after it had to be done over amid controversy.

In his note Friday, Clark did not mention any new role he may take after Amazon.

“For some time, I have discussed my intent to transition out of Amazon with my family and others close to me, but I wanted to ensure the teams were setup for success,” Clark wrote. “I feel confident that time is now.”