Open-source database provider 10gen has raised $3.4 million in a Series B round of funding. 10gen wrapped up its $1.5 million round of Series A funding back in July 2008, with major investments from Union Square Ventures. Union Square contributed once again to the latest round of financing, though Flybridge Capital Partners led the fundraiser this time around.

10gen oversees and provides commercial support for MongoDB, a project dedicated to providing users with a high performance and open source database for Web applications. MongoDB includes support for dynamic queries, query profiling, storage of large data files, and many more vital features for any comprehensive Web database structure.

With three tiers of commercial support, 10gen offers clients a conveniently varied list of options for taking advantage of the company's services. The Basic server costs, at $1000 per server/year, comes with support during regular business hours and a four hour response time. Silver support, at $3000 per server/year, comes with 24x7 support, but the same four hour response time. At $5000 per server/year, Gold support includes 24x7 support and a 1-hour response time.

Prominent news site Business Insider, Disqus, a comments-based startup, and SourceForge, a massive library for free open source software, have already taken advantage of 10gen's database service.