When Jim Freeman, the Alexa VP in charge of messaging products, told Amazon he’s leaving for the German e-commerce company Zalando earlier this year, the higher-ups asked him to stay, according to a person familiar with the matter.

Freeman didn’t budge, and in April he ended up joining the Berlin-based company.

Freeman, who first joined Amazon 9 years ago and previously spent a short time at Zalando, had a lot of support internally, as he oversaw the development of all Alexa messaging features, like audio and video calling. Previously, he also ran Amazon’s entire video team, including Prime Video and Amazon Studios.

Freeman’s departure is part of a recent wave of executive departures at Amazon. Even as Amazon enjoys unprecedented success and record-level stock prices, some of its senior executives are opting to leave. Smaller companies offer fresh opportunities and a relief from its high-intensity work culture, hiring experts say.

More than a dozen executives and senior managers have left Amazon over the past 10 months. Among them, Susan Harker, a VP responsible for global recruiting, took a leave of absence last August, according to people familiar.

Other recent departures that have been previously reported include top executives like Prime boss Greg Greeley and marketplace chief Sebastian Gunningham, as well as lower-level execs like Gene Farrell, a VP at Amazon Web Services, and Tim Stone, a finance VP who joined Snap as CFO earlier in May. Mike George, former VP of Echo, Alexa, and the app store, retired last June after a 20 year-run at Amazon.

In Freeman’s case, this is his second run at Zalando. He had previously joined the company in 2016, only to return to Amazon six months later for personal reasons. The personal issue has been resolved in recent months, and so he insisted on returning to the German company, people familiar with the matter said.

In a statement, Amazon said, “It’s simply incorrect to suggest that we have an executive retention issue. Amazon is the most attractive place to work in the US, according to LinkedIn, and we have nearly 95% retention among our Vice Presidents. For 20 years it’s been the case that a handful of executives have come and gone — for personal or professional reasons — and that’s true at any company. What’s unique about Amazon is that many come back — we call them ‘boomerangs’.”

One tech investor, who declined to be identified due to his close work with Amazon, said some of the departures are driven by a desire to take on bigger roles.

Freeman, for example, is now running all of Zalando’s engineering. Farrell, who left AWS to join Smartsheet, was able to be part of the company’s recent IPO roadshow, an experience Amazon wouldn’t have provided. Jamie Heywood, who was a director at Amazon, is now in charge of Uber’s UK operations. In the case of Stone, the investor surmised he was likely excited about a “turnaround job” at Snap.

Professional recruiters point to two broader trends for the sudden uptick in the number of managers leaving: burnout after breakneck growth and stronger demand for Amazon executives from other companies.

Jim Herd, managing partner at the Seattle-based executive recruiting firm Herd Freed Hartz, said Amazon could be a tough place to be for a long time, as its work culture tends to be more fast-paced and high-pressure than some of its peers.

“When you go to Amazon, you’re on a treadmill — it’s really non-stop,” Herd said. “It’s not a place for everyone.”

At the same time, thanks to Amazon’s exponential success in recent years, the demand for Amazon executives has grown significantly, Herd said. Now, 9 out of 10 of his clients pick Amazon as their most preferred poaching destination, he said.

And the higher Amazon’s stock goes, the more companies are asking for Amazon executives to come help build a similar culture of growth. It is no coincidence that a lot of the departing executives went on to join later-stage startups, such as Airbnb, WeWork, and Uber, he said.

“In the ’90s everybody wanted Microsoft executives. Now it’s Amazon,” Herd said.

One Silicon Valley recruiter, who declined to be identified due to his work with Amazon, said there’s been more demand for Amazon executives in recent years following the breakout success of AWS and Alexa voice technology. Those two businesses have transformed Amazon’s image from a simple online retailer to a more sophisticated tech company, stacked with talented engineers in emerging areas like machine learning and artificial intelligence, this person said.

“Amazon is now in so many areas that’s relevant to so many people, it’s become an obvious hunting ground for any client in the tech space,” this person said.

Amazon’s representative wasn’t immediately available for comment.

As a result, Amazon executives are drawing lucrative offers worth millions of dollars, these people said. Case in point: Stone, Snap’s new CFO, received a total compensation of $20 million — the equivalent of the salary for the 63rd highest paid CEO among the largest US companies last year, or the same amount as Microsoft CEO Satya Nadella.

But not everyone enjoys a big payday by leaving Amazon. Some people are forced to take a pay cut to go work at a smaller scale company, where they can exert more control over business decisions, said Max Hansen, CEO of recruiting firm Y Scouts.

He said Amazon has become so big — now with over 560,000 total employees — that it’s almost impossible to make big decisions that really “move the needle.” And for people that crave a more hands-on experience, the change comes with a cost.

“They’re willing to take less money for a role that creates a bigger impact,” Hansen said. “A lot of these people feel like they can’t show their individuality at Amazon.”