Dwight Merriman via Business Insider

10Gen is not a startup you hear discussed often at cocktail parties, even the kind full of engineers. But Kevin Ryan has told Betabeat on more than one occassion that he believes 10Gen --which provide commercial support for MongoDB,  the increasingly popular open source NoSQL database-- is the AlleyCorp company with the most potential in the long term.

10Gen has just raised a $20 million series D from Sequoia, FlyBridge and Union Square Ventures.

The company is run by Dwight Merriman, who along with Kevin O'Connor, founded the ad-tech company that would become DoubleClick. Mr. Merriman is widely acknowledged by both Kevins as a technical genius, the kind of person who can handle a complex, rapidly evolving database play in the enterprise space.

According to GigaOm, 10Gen now has over 400 customers and more than 100,000 downloads of its MongoDB package per month. While that doesn't sound huge by consumer standards, it's proof that MongoDB is more than just a fad. If growth continues apace, the NoSQL system could be a serious player in the massive multi-billion database industry. Clients already include big names like Disney and Viacom.

10Gen hopes to use the funding for international expansion and building out the capabilities of MongoDB.