Meteor, a well-funded member of Heavybit‘s stable of developer-centric startups, today announced that it has acquired FathomDB and its database technology.

FathomDB was a Y Combinator startup that set out to build a fault-tolerant and scalable relational database service. The company was founded by Justin Santa Barbara, who will join Meteor and continue to work on FathomDB. The service launched back in 2009 (it’s a member of the YC Winter 2008 class) and at the time used Amazon’s EC2 service for hosting its databases.

It’s hard to say how well the company did over the years, though, especially given that Amazon launched its own cloud-based database service shortly after FathomDB went online. FathomDB partnered with Rackspace and others, too, but it never raised any follow-up funding after Y Combinator (or at least never disclosed it) and it’s been very quiet around the company for years.

FathomDB still supports both AWS and Rackspace today to automate database backups and monitor performance in real time. As Meteor co-founder Matt DeBergalis described it to me, the company believes that FathomDB will be far more successful as a part of this larger platform. Companies like FathomDB, he argued, “are incredibly hard to build and very difficult to monetize.”

Meteor, on the other hand, is doing very well. It’s under heavy development, and there are now plenty of companies that have raised more than $7 million each that run almost completely using the Meteor framework.

With the technology from FathomDB, Meteor — which is centered around JavaScript and Node.js, as well as MongoDB as its database — gathers a number of new features for its developers. Specifically, DeBergalis said, the team isn’t so much excited about Fathom’s NoSQL and MySQL capabilities, but about its ability to watch how data changes and then push those changes out to users — both on the web and on mobile.

That’s a piece Meteor was still missing. “When you build a modern app,” DeBergalis said, “you need to be able to work with data in real time and move that data to browsers and mobile devices. That’s a piece of the puzzle that you don’t get with MongoDB by default.”

Meteor developed some tools for this itself, but it hopes the FathomDB technology will allow it to improve support for reactive queries in both MongoDB and other databases engines.

The Meteor team is currently preparing the platform for general availability, DeBergalis tells me, and the current expectation is to launch version 1.0 later this year — most likely even before Thanksgiving. At that point, the project will be able to offer businesses a stable API to work with. Many of FathomDB’s features will become part of this 1.0 release, it seems, but maybe even more importantly, they will become part of Meteor’s commercial offering, too, which will launch soon.

What exactly will happen to the standalone version of FathomDB, however, remains to be seen.