Houston founder shares how he's using tech to make digital media more effective and equitable

houston innovators podcast episode 173

This month, Mark Walker is celebrating his company's one year anniversary of going public — only the ninth Black-founded business to accomplish this feat on a U.S. stock exchange. Photo courtesy

After working in both sides of the advertising world, Mark Walker thought he could reimagine a platform that would be more efficient and equitable.

Walker co-founded his company, Direct Digital Holdings, an adtech platform, after serving in several roles — from an early hire at Houston digital media startup Questia to business development director at NRG Energy and COO of EBONY Media. He shares on the Houston Innovators Platform how he took this experience in tech, advertising, and media to create his company's platform.

"NRG Energy gave me a top-down view of the value chain, and Ebony gave me a bottoms-up view of the value chain of how media is purchased," Walker says on the show. "At Direct Digital Holdings, we help companies buy and sell media — and we leverage technology to do it. It's really the culmination of both of those experiences."

With over 30,000 publishers on its platform, Direct Digital makes it easier for its core customers — middle market companies looking to buy into the digital media ecosystem — to tap into these opportunities without the tech know-how they might otherwise need. Walker explains that at EBONY, he saw how small to midsize publications — especially the multicultural ones — were being left out on the ad selling side of the equation. The Direct Digital platform bridges the gap on each end.

Founded in 2018 in partnership with Keith Smith, who went through similar professional experiences, Direct Digital went public exactly one year ago after growing the company through strategic M&A activity. Walker says the decision to IPO made the most sense for his company — though it wasn't an easy process. Direct Digital is only the ninth company founded by a Black entrepreneur to go public on a US stock exchange.

"If you think the process is hard — it actually is," Walker says on the journey to IPO. "We were a privately held company, and we knew we had a good growth trajectory and we looked a couple different options. We decided to go public in a very traditional way."

Walker explains there were some risks involved, but the co-founders ultimately decided to shy away from adding in investors who might not have the same ideas for the company's future.

Direct Digital has been a Houston company from the star — despite the city not being home to a booming adtech ecosystem. Instead, Houston — with its collection of Fortune 500 companies and rich diversity — has allowed the business to stand out.

"If you look at and reflect on how our company has been built — from our board of directors to our leadership and management team — we're a majority minority organization all the way across the board," Walker says. "Diversity is very important to us. It's the lifeblood of our business — especially because we're serving publishers in those communities in big way. And moreso, we think you get the best product, thoughts, and ideas from a diverse workforce, and Houston fits right into that mold for us."

Walker shares more about his company's future, advice on IPO, and what all he's watching in adtech — from AI to streaming — on the podcast. Listen to the interview below — or wherever you stream your podcasts — and subscribe for weekly episodes.


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Uber, Nuro and Lucid plan to roll out robotaxi services in Houston

autonomous autos

More autonomous vehicles are expected to hit the roads in Houston next year.

Ridesharing giant Uber announced that it plans to roll out its premium robotaxi service in the Bayou City in mid-2027. Houston will be Uber’s second planned market for the program, following the San Francisco Bay Area, where the program is expected to be rolled out later this year.

Uber, Nuro and Lucid Group will bring the robotaxi program to Houston with more markets planned for the future. Currently, Nuro is conducting autonomous on-road testing with safety operators in Houston. Testing includes simulation, closed-course testing and supervised public-road testing.

“Houston is a city Nuro knows well, and we’re excited to help bring this robotaxi service to the city through our partnership with Uber and Lucid,” Andrew Chapin, chief operating officer at Nuro, said in a news release. “Houston’s large, complex metro area is an ideal market for demonstrating how Nuro’s universal autonomy platform can generalize across different geographies and operating environments. We look forward to continued engagement with the community as we prepare to launch service in 2027.”

The fleet of 100 vehicles across California and Texas will feature Lucid Gravity EVs and future Lucid Midsize vehicles equipped with Nuro Driver technology, Nuro’s Level 4 universal autonomy platform, plus a redundant sensor suite with cameras, lidar, radar and a roof-mounted halo.

The vehicles will be owned and operated by Uber and its fleet partners and made available to riders through the Uber network, according to the company.

In addition to the fleet of autonomous vehicles, Uber also announced that it has secured a 50,000-square-foot depot facility and dedicated charging pitstop in Houston. The facility will allow Uber and its partners to control vehicle maintenance, repairs, charging, cleaning, and day-to-day operations.

“Houston marks an important next step in our partnership with Lucid and Nuro as we expand autonomous mobility to more riders throughout the world,” Sarfraz Maredia, global head of autonomous mobility & delivery at Uber, added in the release. “Together, we’re combining best-in-class vehicle and autonomy technology with Uber’s scale, fleet operations expertise, and infrastructure capabilities to build a service that can grow across dozens of markets in the years ahead.”

Waymo launched its autonomous vehicle program in Houston in February.

The company later suspended its driverless car services in Houston, other major Texas cities, and Atlanta, after one of its vehicles was stranded by flooding during heavy rains. However, according to the Houston Chronicle, the fleet has resumed activity in Houston and is fully active.

Houston fintech company closes $7M funding round

fintech funding

Houston-based fintech company Receipts Depositary Corporation has closed a $7 million oversubscribed funding round and plans to scale.

The round was led by Austin-based LiveOak Ventures, with participation from Hivemind Capital, Onigiri Capital, OTC Markets Group, GTS, and Redbeard Ventures, according to a release from RDC.

RDC's platform issues depositary receipts (DRs) to qualified investors on digital and alternative assets, making it easier for investors to buy and trade hard-to-access and less traditional assets. Currently, the company offers DRs for cryptocurrencies including Bitcoin, Ethereum, Solana and XRP.

RDC says the new funding will allow it to launch new DR products across a wider range of asset categories, potentially including commodities. Additionally, it plans to grow its relationships with "banks, broker-dealers, market makers, custodians and exchange partners" and add to its product, operations, technology, and commercial functions teams. The company is actively hiring, according to a press release.

“Depositary Receipts are trusted, regulated capital markets products which RDC is bringing to an entirely new universe of assets, from commodities to digital assets, that have historically been out of reach of traditional securities markets," Krishna Srinivasan, founding partner at LiveOak Ventures, said the release. “The team's depth of experience in the DR business on a global scale, combined with the broad institutional validation from co-investors, anchor customers, and strategic partners across asset classes, makes RDC uniquely positioned to define this category. We're proud to lead this round and support the company as it scales.”

RDC was founded in 2022 by three Citibank alumni: CEO Ankit Mehta, CEO Bryant Kim and COO Ishaan Narain. It began offering its first DRs for Bitcoin in 2024.

“This funding round is a strong validation of what we’re building at RDC and the growing demand for modernized Depositary Receipt infrastructure,” Mehta added in the release. “With the support of LiveOak Ventures and our investor partners, we are accelerating development across our DR platform expanding our market reach, and building the team needed to support the next generation of DR product

Houston space co. adds local colleges to university alliance

space schools

Houston’s Axiom Space has added 26 new members to its University Alliance—including two from Houston—to support the next generation of space exploration.

Engineers, researchers and students from the partnering universities will be dedicated to advancing microgravity research, technology development and commercial innovation in low-Earth orbit.

Rice University and the University of Houston are among the new colleges to join the alliance, which launched with 15 members last year. The University of Texas at Austin and the University of Texas at El Paso have also joined, in addition to international institutions in Europe, Asia and Australia, and others from around the U.S. See full list here.

“Through the University Alliance, Axiom Space is uniting the international research community driven to enable human progress,” Lucie Low, Axiom Space chief science officer, said in a news release. “Together, alliance members are taking the initiative to ensure microgravity research benefits everyone on Earth and our shared goals fulfill a scientific purpose to advance civilization.”

Axiom is building the world’s first commercial space station, known as Axiom Station. The University Alliance “will support and advance space science during the transition from government-led to commercially owned and operated space stations,” the company said in a release. Partnering universities will contribute to the research community by participating in international collaborative scientific initiatives, identifying future research, and bolstering strategic positions in the commercial orbit research field.

Recently, the Rice Space Institute was also selected to lead the U.S. Space Force Strategic Institute 4 in addition to other space-centric partnerships.

“We’re excited to bring our expertise to this global alliance and to benefit from the deep expertise of our partners,” David Alexander, professor of physics and astronomy and director of the Rice Space Institute, said in a news release. “Space is truly a collaborative and global endeavor. Alliances like these are key to progress.”

UH and NASA’s Johnson Space Center expanded their collaboration in 2022. In 2024, UH launched its NASA MIRO Inflatable Deployable Environments and Adaptive Space Systems Center (IDEAS2) via a five-year, $5 million grant.

“As a major public research university located in Space City, the University of Houston has a unique opportunity and responsibility to help lead the future of space innovation, and our participation in Axiom Space’s University Alliance represents a major step forward in that mission,” Karolos Grigoriadis, the Hugh Roy and Lillie Cranz Cullen Endowed Professor and chair of mechanical and aerospace engineering at UH, added in a separate release.

Meanwhile, Axiom recently tacked on an additional $175 million to a previously announced capital raise, bringing the oversubscribed round to a total of more than $525 million. It also has announced plans to launch Swiss and Japanese subsidiaries.

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