Soon, Jassy will take on his biggest role yet: Amazon CEO. On Tuesday, the company announced that he will take over from founder Jeff Bezos, the modern-day Andrew Carnegie, who is stepping aside.

Jassy, who has been a key player, but one who has worked largely in the background, will have huge shoes to fill. He’ll control everything from Amazon’s huge online retail business to movie making to a growing air cargo business.

While he’s proved himself as capable of leading a cutting-edge technology provider, Jassy’s leadership skills will be rigorously tested as he steers the company at a crucial point in its history. Rival retailers are all-in on closing the gap with Amazon while regulators increasingly scrutinize the company’s octopus-like business.

Jassy joined Amazon back when it was mostly known for selling books, starting as a marketer. But he made a name for himself at the company when he was appointed in 2006 to lead the firm’s cloud computing unit, Amazon Web Services, or AWS. 

When AWS debuted, cloud computing was considered a pie-in-the sky idea. Many analysts and businesspeople dismissed the notion of a company selling computing power to other firms in a pay-as-you go model, partly because the technology required was so cutting edge.

But the idea turned out to be revolutionary. AWS became a $35 billion-a-year-business, selling the data center technology that enabled startups like Uber and Airbnb to quickly develop into technology giants.

“Not only did he take an obscure concept like cloud computing and turn it into the biggest, most important technology trend in the last decade or so,” says Gartner vice president Ed Anderson. “But he also created a business model around it that not only works for Amazon as a company, but for customers.”

Although Jassy had no formal training in computer science, he’s earned a reputation as a rare executive who understands complicated technology and can explain it to business laypeople. At Amazon’s annual cloud conference, Jassy’s on-stage presentations sometimes lasted three hours, as he detailed new AWS services and how those tools could help businesses. 

“He’s very astute when it comes to understanding customers and understanding markets and the dynamics that are driving [business] decisions,” Anderson says.

A big challenge facing Jassy in his new role, however, is his lack of experience heading a giant consumer business, says Ron Josey, an analyst for JMP Securities. But because Bezos will take the title of Amazon’s executive chairman, Josey believes that Bezos will be able help Jassy adjust.

And even though he hasn’t led a consumer-facing business, Jassy has been a trusted member of Bezos’s inner circle. He’s therefore likely to know more about running a consumer-facing company that many people may assume, Josey explains.

Andrew Lipsman, an eMarketer analyst, says Jassy and the recently retired former Amazon retail chief Jeff Wilke, are “great lieutenants.” At one point, Jassy and Wilke were both CEOs of Amazon divisions, leading the cloud and retail units respectively with Bezos acting as a sort of uber-CEO role. Both Jassy and Wilke “would easily be able to pick up the ball” in Bezos’s absence, Lipsman says.

Lipsman compared Jassy taking over Bezos’s CEO role to Apple CEO Tim Cook replacing the legendary Steve Jobs. Although people questioned whether Cook would be a worthy successor to Jobs, Cook’s expertise as a skilled operator—akin to Jassy—proved instrumental in leading Apple to record sales.

“The whole ethos of the company, how they use data, how they are so deliberate in how they go after pockets of opportunity, I think Andy Jassy is a big part of it,” Lipsman says. 

Jassy’s skills as an operator will come in handy as Amazon develops its logistics and delivery businesses, which will require similar managerial skills as leading the company’s wonky cloud computing unit, Lipsman adds.

Jassy’s new role may also help Amazon with regulators, who have already launched antitrust investigations into Google and Facebook, says JMP’s Josey. It gives Amazon “a fresh face” in Washington D.C. at a time when Bezos has become a lightning rod.

Josey likened Jassy’s CEO appointment to Google CEO Larry Page being replaced by Sundar Pichai, who also has a low-key image.

Indeed, Jassy is no stranger to the federal government, as Josey noted. AWS has built a substantial government cloud business that really kicked off in 2013, when the CIA contracted with AWS to build its a custom cloud computing facility, he says.

With Amazon continuing to record huge sales, Lipsman believes that Jassy will help the company dominate. 

“I think their next five years are well mapped out already,” Lipsman says. “I don’t think there’s necessarily lots of ways to screw it up.”