All it took was one tweet for Ryan Graves to grab the attention of Travis Kalanick and Uber. REUTERS/Beck Diefenbach Ryan Graves' career at Uber began with a tweet.

In January 2010, when Uber was less than a year old, Travis Kalanick, then the CEO, tweeted: "Looking 4 entrepreneurial product mgr/biz-dev killer 4 a location based service.. pre-launch, BIG equity, big peeps involved—ANY TIPS??"

Graves saw Kalanick's tweet and responded: "Here's a tip. email me :)". He included his email address, too.

Graves has since left Uber, but his unconventional job application led him to one of the longest-running tenures at Uber — he even outlasted Kalanick, who resigned as CEO in 2017.

Graves most recently served as the company's senior vice president of global operations, but he held several positions at Uber, even briefly serving as CEO before handing the reins back to Kalanick in 2011.

"Ryan Graves' first day was March 1st and he hit the ground running," Kalanick wrote in a blog post detailing Uber's origins. "From the day he got going, we spent about 15-20 hours a week working together going over product, driver on-boarding, pricing model, the whole nine. He learned the startup game fast and worked his ass off to build the Uber team and make the San Francisco launch and subsequent growth a huge success."

From working for free to $1.58 billion

In 2010, Graves' work experience included a database-administrator position at General Electric and a stint in business development at Foursquare, which he got by working for the company for free after it initially turned him down.

Kalanick presumably followed up with Graves after his initial tweet, and Graves became Uber's first hire. Graves was known throughout his time at Uber as the "Mr. Nice Guy" in contrast with Kalanick's aggressive personality, and he was said to be well-liked by his peers both within Uber and the larger tech community.

Chris Sacca, an early investor in Uber, wrote several glowing tweets about Graves following the news of Graves stepping down. Graves and Sacca are longtime friends — Graves and his wife even spent the night at Sacca's house before Graves started at Uber.

Graves is "the director most consistently respected by the others and is great at building consensus," Sacca wrote.

Kevin Rose, another investor, also tweeted his support:

Graves was noticeably absent throughout Uber's tumultuous 2017. He transitioned to a new "resident builder and entrepreneur" role in 2016, and multiple people told Business Insider in March 2017 that Graves wasn't often seen around the office for long stretches of time and seemingly had a decreased role in the company.

These days, Uber's $75.5 billion initial market cap as the company goes public on Friday makes Graves a paper billionaire.

Graves has committed to donatingat least $14 million in Uber shares to charity through the global nonprofit charity: water, which wants to end the water crisis by providing clean water to communities in need.

Maya Kosoff contributed to an earlier version of this story.