Last August, I wrote a piece for Forbes laying out five reasons why retail media networks hide their tech stacks from the very brands they want to attract: shame, financial narrative control, the knowledge gap, margin protection, and fear of being copied.

I polled verified brand-side buyers alongside the piece: does knowing a retailer's ad-tech stack influence your spending decisions? 88% said yes.

Then in January, Costco's Mark Williamson, AVP of retail media, walked on stage at an NRF side event and put his entire tech stack on a series of slides -- in front of customers, observers, and competitors. It was a bold move, underscored by the fact that nearly everyone in the room raised their phones to photograph it. [I wrote about it here.] 

Last week, I hosted a livestream with Williamson and Jon Flugstad, Chief Business Officer at MetaRouter (who sponsored the livestream) to talk, in part, about how such transparency is working out at Costco Velocity, the new name for the network. 

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The ‘original sins’ of retail media

Williamson has been in retail media for 15 years, across Sam's Club, Ahold Delhaize, Epsilon, and CitrusAd. He's been the insecure RMN leader who didn't want to talk about his platform.

"I've been one of those people that's been insecure about my platform," he said. "I've been ignorant of my technology partners. And that does put you at a disadvantage when you're trying to have a JBP conversation with a supplier, or you're talking with an agency and you just don't feel confident in your stuff."

Costco was never going to win on digital innovation credentials — "we're not gonna win any hackathons," as Williamson put it. So they'd win on honesty about what they're building and where the gaps are.

That was also driven by Costco's code of ethics, which includes "respect for the supplier." 

"At the end of the day, we are doing partnerships with people that supply goods to Costco that our members love. I feel like it's our obligation to respect them enough to tell them what we're doing and how we're doing it."

Transparency as a practical tool

When Costco says no to a capability request, they can point to the stack and explain why — and when it might become a yes.

"If we say no to something, we can point to and say, this is why it's no, or maybe this is why it's not yet. Because we haven't connected this box with this box, but that's where we're gonna go."

Most RMN leaders dodge capability questions or overpromise on the roadmap. Costco's tech stack has become a shared reference point between the media team, merchants, and brand partners.

Costco has made it a requirement for new tech vendors to explicitly commit to working with their existing identity and data layer. One of the first questions they ask any prospective partner: have you integrated with MetaRouter?

MetaRouter is their data and identity layer — it captures behavioral signals from Costco's digital properties, resolves them to a member identity, and distributes that data to whatever activation or measurement tool needs it. Crucially, Flugstad noted, MetaRouter deploys inside Costco's own virtual private cloud — member data never leaves Costco's environment. That matters because one of Williamson's earliest decisions was a set of non-negotiable data principles: own the data, minimize data movement, minimize data copying.

Costco also benefits from timing. Five years ago, the vendor landscape was thin — CitrusAd, Criteo, PromoteIQ, LiveRamp, The Trade Desk, Meta, and not much else. Now there's modern tooling built for different approaches. As a late mover, Costco gets to build from scratch rather than retrofitting stacks assembled under pressure. Flugstad called this a "built-in arbitrage opportunity."

But Williamson was quick to say that it hasn't been easy or cheap. He's been in the role for about two and a half years — long enough to have momentum, but "in Costco years, I am an itty bitty infant." Nothing was turnkey. Costco's data was fragmented across disparate systems, with identifiers that had nothing to do with the actual member. Getting approval to access, organize, and use that data meant jumping through hoops at every step — legal, privacy, policy.

"That friction forced a lot of clarity in the vision," Williamson said. "It's taken longer, it's cost more money, and it's been way more complicated than it needs to be. But it had to be this way for it to work."

The path to unlocking the power of Costco's data had to be a uniquely Costco journey. The company runs what most people experience as one store but what internally operates as roughly ten different businesses — ecommerce, warehouse, same-day, Costco Travel, tires, fuel — each with its own systems and P&L. Stitching those together at the member level is the foundational work that everything else depends on.

Two new moves that the stack enables

Onsite is the biggest part of Costco's retail media business, but until last week it was the least sophisticated. Display placements were static, non-targetable, and couldn't connect ad exposure to warehouse sales. Brands were operating largely on faith.

Last week, Costco Velocity announced a partnership with Moloco Commerce Media, which starts with Reserved Display — a new onsite format where Moloco's AI engine, trained on Costco's first-party data, matches ads to individual members. The Moloco ad server plugs into the full Costco Velocity stack, so it knows everything Costco knows about that member. Reserved Display will run alongside Criteo-powered sponsored product ads. 

Costco Velocity also announced a deal with Symbiosys that lets advertisers promote Costco-available products in Google Shopping search results. Williamson sees this as groundwork for wherever search goes next. "Google today, ChatGPT tomorrow, perhaps," he said.

The honest gaps

Costco's internal North Star is the membership renewal thesis: better retail media drives more conversion, which drives higher renewal rates. It's unmeasured. The technology has historically operated at visitor level, not member level. The Moloco and MetaRouter integrations should start to close that gap, but haven't yet.

Several components of the stack are early. Self-serve for display is new. The Symbiosys partnership is new. Building in public earns credibility — but everyone can see what's not yet finished.

What this means for the rest of the field

Is Costco's transparency changing advertiser behavior, or is it good PR? Probably both. When 88% of brand-side buyers say a retailer's tech stack influences spending decisions and one retailer is bold enough to bare it all, that retailer picks up a disproportionate share of curiosity and pilot budgets.

Most retailers are still hiding. The five reasons I outlined last August haven't gone away. But Costco's experience points to something I didn't cover then: transparency makes the internal job easier too. It forces clarity. It creates accountability to a public roadmap. And it gives the retail media team a shared language with merchants, brands, and technology partners that opacity can't.

"It actually makes it easier to tell our story when you have nothing to hide."

Watch the full replay of the livestream here on LinkedIn. 

Subscribe to Costco Retail Media’s “The Buck Fifty” newsletter on LinkedIn.

PS — I’m hosting another informal Happy Hour in Atlanta next Wednesday, April 1st. JOIN US!

No pitching, no pressure — just a casual drink with ~20 of your new commerce media besties 🙂 This happy hour is proudly sponsored by GrowthLoop.