The new man in the driver's seat of global ride-sharing giant, Uber, was born in Teheran and only nine when his family fled the revolution that rocked their native Iran for the United States in 1978. That alone makes Mr Dara Khosrowshahi a sharp contrast to the man he was chosen to replace just a week ago.

As Bloomberg View notes, he brings with him a "reputation for low-key level-headedness".

The man he is replacing as chief executive, Uber founder Travis Kalanick, by contrast, brandished a brash personality more typical of his history as a California-born and bred entrepreneur, one that spawned what The New York Times describes as Uber's "aggressive, unrestrained workplace culture".

Although that enabled Mr Kalanick to turn a company that put a taxi ride at everyone's fingertips into a US$70 billion (S$95 billion) success story in a little more than seven years, it nearly crashed last year, racking up losses of almost US$1 billion in the final quarter and shedding another US$645 million in the second quarter this year as it navigated a series of crises that led to Mr Khalanick's ouster in June.

Board members are counting on Mr Khosrowshahi, 48, to turn that around and, while the first words he wrote last week in announcing his move might have unnerved them a bit, it showed just how different a man he is: "I have to tell you that I am scared."

As Reuters noted, observers portray him as distinctly different from Mr Kalanick - "calm, low-key and measured". One person who has worked with him said he is not the "call you and scream kind of guy".

Still, what might seem like a tall order for anyone else entering a new corporate culture built on screams seems like no great shakes for a man like Mr Khosrowshahi. Like any immigrant, especially from a country that turned hostile to the US, he faced discrimination.

"We sure didn't feel like refugees, but in hindsight I guess we were - my father and mother left everything behind to come here - to be safe and give their boys a chance to rebuild a life," Mr Khosrowshahi wrote of his early years.

There were other challenges growing up in Tarrytown, New York too. "My father had to go back to Iran to take care of his father when I was 13 and was detained for six years before returning," he told Bloomberg. "My mum was raising three kids without a dad."

Yet the youngster not only overcame that and survived a radically different country's culture at such a tender age, but he also thrived.

After high school, where he became captain of his high school soccer and lacrosse teams, he went on to train as an engineer at Brown, an Ivy League university. After that, he spent years at American media and Internet company IAC as chief financial officer and in various operational and strategic roles.

Then, as Uber describes him in a memo: "In 2005, he became CEO of Expedia, which he built into one of the world's leading travel and technology companies, now operating in more than 60 countries."

By 2015, Mr Khosrowshahi had done what most native-born Americans never do - earned nearly US$95 million that year in total compensation for his efforts.

The board went on to call its new CEO "the best person to lead Uber into the future, building world- class products, transforming cities, and adding value to the lives of drivers and riders around the world".

Notably, it said his appointment was also aimed at "improving our culture and making Uber the best place to work". Indeed, his first big challenge will be to repair a corporate culture that has been described as a veritable boys' club, resulting in lawsuits and executives leaving in droves. The Financial Times called it "a toxic culture that was rife with sexism and harassment".

At Expedia, Mr Khosrowshahi advocated for women getting equal pay and leadership opportunities.

His background could also make him good for Uber's future in Asia. "The kind of partnerships we need in South-east Asia are going to be easier with someone like him at the helm," said Mr Bradley Tusk, an Uber investor and adviser, in a Reuters interview. "He encompasses a lot of the balance that we need that we weren't getting with the other candidates."

Indeed, Mr Khosrowshahi's wife Sydney Shapiro said "yes" to his marriage proposal while they were on a trip to Cambodia's Angkor Wat temples. Married in 2012, they have four children.

And while, his no-nonsense reputation might imply they are boring, the couple is anything but. His bride reportedly wore a Slayer - a hard metal rock band - T-shirt down the aisle. "That tells you what kind of woman I'm lucky enough to be with," he told Bloomberg.

Mr Khosrowshahi donned an Uber T-shirt instead of a jacket and tie when introduced to workers at last week's "all-hands" gathering in Uber's San Francisco headquarters, according to photos posted online. There, he promised his new troops both change and transparency - and challenged them in the process.

"This company has to change. What got us here is not what's going to get us to the next level," he reportedly said in tweets posted by employees. "If culture is pushed top down, then people don't believe in it. Culture is written bottoms up."

Then he told them: "I'm a fighter. I'm all-in and I'm going to fight for you with every bone in my body."