Toward the tail end of his 28-year career at Goldman Sachs, Don Duet was running the bank’s technology division and helping lead investments in emerging companies including Square, Docker and Barefoot Networks.

Duet retired from Goldman earlier this year, but far from hitting the beach, the ex-banker has gone from investing in start-ups and deploying their technology to working at one. He’s now chief operating officer at Vapor IO, a 25-person company in Austin, Texas, that raised money from Goldman in 2015.

Vapor, whose technology is designed to give cell towers the power of massive data centers, was founded by Cole Crawford, the former executive director of Facebook’s Open Compute Project. Duet was a director at the project, which was started in 2009 by engineers from Facebook to create more efficient data center infrastructure that could handle the explosion in new types of data.

“Cole and I have known each other for many years and had an ongoing dialogue” about potentially working together, Duet told CNBC.com. “It became a very interesting opportunity.”

Duet said one of the main things that got him excited was an investment from Crown Castle, the owner of 40,000 cell towers across the U.S. The size of the deal hasn’t been disclosed, but Duet said it’s a minority investment and part of a funding round that is still in the works and will include other backers.

The Wall Street to Silicon Valley path has become a familiar one in recent years. Anthony Noto led Twitter’s IPO at Goldman and then joined the internet company as CFO in 2014. Ruth Porat left her position as finance chief at Morgan Stanley in 2015 to take that role at Google. Ned Segal, a former Goldman tech banker, became CFO of RPX in 2013 and then joined Intuit as a senior vice president two years later.

Duet isn’t exactly charting the same course, since Vapor is based in Austin and he’ll continue to work remotely in New York. But the bigger difference is that he’s a technologist, not a finance guy.

Duet is joining Vapor as the company introduces “Project Volutus” to enable cloud providers and wireless carriers to take advantage of “micro data centers at the base of cell tower sites.”

Vapor is out to solve the “last mile” problem of high-speed computing. Massive data centers tend to sit in areas where land is cheap and real estate is plentiful, but data-intensive applications like autonomous cars and virtual reality need to be close to servers for rapid response times.

“We’re really moving compute to the bay stations,” Duet said. “We’re helping change the way that information and data moves through the internet.”