Mirantis, one of the last pure play OpenStack startups left standing announced a major win today when VW chose them over Red Hat for an enormous OpenStack implementation.

It was huge for Mirantis and for the open source OpenStack project. VW knew it wanted to run a private cloud on OpenStack. The only question was the vendor. After a call for requests for proposals it came down to two: Mirantis and Red Hat.

The project is massive involving dozens of data centers and tens of thousands of nodes, according to Boris Renski, CMO and co-founder at Mirantis.

VW decided to take the private cloud route because it saw a couple of problems with public cloud offerings including a lack of features it specifically needed for its use cases, Mario Mueller, corporate director of IT operational services and infrastructure technologies at Volkswagen Group told TechCrunch.

“Given the scale of our use case, we knew we [would] need to have a private cloud at some point. We also knew that private cloud would require more work. As we pursue digital transformation at VW group, we aim to tackle the hard problems first. Public clouds today feature a broad range of infrastructure services and go horizontal across all industries, because of that when it comes to large-scale vertical use cases (like automotive cloud for VW Group) the economics don’t work as well,” Mueller explained.

VW put its finalists, Red Hat and Mirantis through their paces with 63 small pilots and use cases they had to solve on the fly at VW headquarters working in groups in separate rooms throughout the process.

“It was an extremely rigorous process. We had two weeks to complete all of the tasks and a week to present them to the VW team,” Mirantis VP of worldwide sales Marque Teegardin said. VW judged the two vendors purely on technical merit based on how well they solved each task based on VW’s technical requirements.

In the end, Mirantis scored highest and won the project. When asked if such a large project might be a strain on a startup, Renski pointed out while it was a big accomplishment it wasn’t the first large customer implementation it’s pulled off as a company. Other enterprise customers include AT&T (which has Mirantis running in 74 data centers), Ericsson and GAP.

As for Red Hat, when asked for a comment, Margaret Dawson, head of global product marketing for cloud solutions at Red Hat took the high road, preferring not to address this specific deal directly.

“Overall, we want OpenStack to win as the private cloud infrastructure of choice for telco, enterprise and government. This is a huge market, with 451 Research forecasting OpenStack to be a $2.5B opportunity by 2017, so we welcome and need a healthy OpenStack market ecosystem,” she told TechCrunch in an email.

OpenStack, the open source private cloud project created in 2010 by NASA, Rackspace and others as a check against AWS’s growing power, has spawned a slew of startups and attention from the world’s biggest companies from Red Hat to IBM to HP to Oracle among others. While many early startups have been sold or even gone out of business in one high profile case, Mirantis is hanging in and securing wins against the some of the biggest traditional IT vendors.

Mirantis has raised $220 million since it was founded in 2011. The most recent round was $100 million last August.