SEATTLE – In 2002, Andy Jassy, ​​a young manager at Amazon, began closely following Jeff Bezos, the founder of the online bookstore.

Mr. Jassy followed Mr. Bezos everywhere, including board meetings, and participated in his phone calls, said Ann Hiatt, who was Mr. Bezos’ executive assistant from 2002 to 2005. The idea, she said, was for Mr. Jassy to be “a brain-double” for Mr. Bezos so that he can challenge his boss’ thinking and anticipate his questions.

“I thought I had very high standards before I started this job,” said Mr Jassy in a podcast interview last fall over the 18-month period alongside Mr Bezos. “Then, with this shadow job, I realized that my standards weren’t high enough.”

Now Mr Jassy, ​​who had learned from Mr Bezos for more than two decades, was accused of having advanced the Bezos Way. This summer, the 53-year-old will take over the running of Amazon while the 57-year-old Bezos is stepping down to become chairman of the board.

Only a few corporate succession are observed so closely. Mr. Jassy has Amazon – which grew into a $ 1.7 trillion company with 1.3 million employees and worldwide operations in e-commerce, logistics, cloud computing, entertainment, and devices – under the watchful eye of Mr Bezos controls who is still the largest shareholder.

Amazon, which has seen a surge in growth, is also facing growing challenges. In Europe and the US, the Seattle-based company is being scrutinized for power by regulators and lawmakers. The own workforce has become louder and more active in dealing with the company. And given its size, some investors and employees are wondering if Amazon can keep its innovative ways without bureaucracy blocking them.

Mr Jassy has not spoken publicly about his vision for Amazon, but those who know him said it was clear he would continue what Mr Bezos had built – and not take a sharp break from it. The quintessential Amazonian life, Mr. Jassy helped design and proselytize many of the mechanisms and internal culture of the company.

“Andy is an integral part of the overall culture,” said Tom Alberg, managing partner of Madrona Venture Group and board member of Amazon through 2019. “I really think this will be a strong sequel.”

Amazon declined to make Mr. Jassy available for an interview. In an email to staff on Tuesday announcing the transition, Mr. Bezos said, “He will be an excellent leader and he has my full confidence.”

Mr. Jassy grew up in Scarsdale, NY, as the middle of three children. His father ran a white-shoe law firm, and his mother ran the household and supported arts organizations. He studied government at Harvard and worked on the business side of The Harvard Crimson, the student newspaper.

Mr. Jassy wanted to become a sports caster, but ended up in direct marketing after graduating. He also tried starting a business with a colleague before going to Harvard Business School.

In 1997 he got the call for an interview on Amazon while going to a Shawn Colvin concert in New York City. He got the job, took his final exam on a Friday, and started working at Amazon the next Monday, three weeks before the company went public, he said in the podcast interview.

After serving in marketing and music, Mr. Jassy was referred to as his “shadow” by Mr. Bezos in 2002, a chief of staff-like role for promising leaders.

“His job was to be an intellectual sparring partner for Jeff,” said Ms. Hiatt, former executive assistant to Mr. Bezos who is now a management consultant. She said Mr Jassy helped Mr Bezos discuss the benefits of offering memberships to the Prime Express Mail program to persuade a skeptical board of directors.

When Mr. Jassy followed Mr. Bezos, he also led Amazon’s step into a new field: cloud computing. At the time, Mr. Bezos was frustrated with Amazon’s software development teams taking longer than expected to complete projects, even though the company hired many new engineers to help introduce products faster. He asked Mr. Jassy to find out.

Mr. Jassy discovered that product teams spent more time designing and building their own infrastructure than developing products. Amazon ultimately decided to reconfigure its technology systems so that different groups could share the same basic technical building blocks.

In 2003, Mr. Jassy and other executives gathered for a meeting at Mr. Bezos’. They said they smelled a business opportunity to help other companies solve the same problems Amazon had encountered.

Before the project could proceed, Mr. Jassy had to present the Amazon board with a “six pager” – a narrative memo that contained a vision for a new idea – and explain what resources would be needed.

“I was so nervous. I wrote 30 drafts of this paper,” Jassy said in a 2017 presentation at the University of Washington.

He asked for 57 people, a meaningful question since Amazon employed about 5,000 people at the time. Mr. Bezos “didn’t flicker,” said Mr. Jassy.

The project became Amazon Web Services, Amazon’s largest source of income. Companies were quick to accept the idea of ​​paying Amazon only for the computers and storage they used, rather than investing large sums in buying, building, and maintaining their own computer systems.

By 2012, Jassy said, Amazon’s cloud entity grew so rapidly that it added roughly the number of computers per day it took to run the entire company in 2003.

Amazon Web Services, known as AWS, ran like a start-up within the company. Mr. Jassy developed a reputation for being tough but not yelling or undercutting staff according to current and former employees. He would ask specific questions in meetings, but would also sit back and let others challenge it while he took in their arguments.

In emails, Mr. Jassy responded to good news by simply saying, “Fine,” with a seemingly random number of exclamation points, said current and former employees. Many debated whether the number of exclamation marks had a secret meaning.

Mr. Jassy also made time for staff activities. He acted as master of ceremonies at an annual Buffalo Wing dining competition known as the Tatonka Bowl. He granted attendees “badges,” one with a burning chicken that appeared in Amazon’s internal directory.

In the past few years, AWS has introduced its own software services that can run on its computers, which is often doomed to failure for startups with competing products.

Corey Quinn of the Duckbill Group, who writes a newsletter titled “Last Week On AWS,” said the cloud computing unit has shown the same intransigence as Amazon’s premier retail website in tracking new products and markets.

“They seem to share a common belief that impossible is only a matter of time,” he said.

Last year, AWS revenue rose to $ 45.4 billion, or 12 percent of revenue and 63 percent of profit for the company.

After becoming CEO, Mr Jassy’s opinions will be examined more closely. Earlier last year he spoke enthusiastically about the sale of Rekognition Police Department, Amazon’s facial recognition technology that has been criticized for bias against dark-skinned people.

“Let’s see” whether police authorities “abuse” the technology somehow, he told the PBS program “Frontline” in February. “They didn’t do that. Suspecting that they will, and therefore you shouldn’t allow them to have access to the most advanced technology out there, doesn’t seem like the right balance to me. “

“I cannot let the death of Breonna Taylor go without accountability,” Jassy wrote in a six-part thread on Twitter about the police in September. “We still don’t get it in the US. If you don’t hold the police accountable for killing black people, we will never have justice and change, or be the country we seek (and claim). “

At an AWS conference in December, Mr. Jassy gave an insight into how he might approach the acquisition of one of the world’s richest tech companies. Echoing Mr. Bezos, who has long been a champion of how businesses need to evolve, Mr. Jassy said the key to long-term survival is for companies to reinvent themselves while business is doing well.

Mr Jassy then put forward an eight-step plan for reinventing businesses, stressing the importance of being “manic, relentless and persistent”.

“You have to have the courage to pull the company up and force it to change and move,” he said.

David Streitfeld contributed to the coverage.