DataStax, one of the most prominent startups in the NoSQL database market, with its focus on the Cassandra open source database, plans to substantially broaden its capabilities through the acquisition of another open source database startup, Aurelius.

Aurelius is the startup behind Titan, an open source graph database. Titan will continue to be available, but now it’s the inspiration for forthcoming commercial software from DataStax, dubbed DSE Graph, DataStax said today.

A column-store-type database like Cassandra can reliably store data across servers in multiple places, while a graph database like Titan depicts the relationships connecting various entities. But while DataStax provides a commercially available distribution of Cassandra, it only had a partnership with Aurelius, DataStax cofounder and chief customer officer Matt Pfeil told VentureBeat.

DataStax customers were “really pushing us to do something” beyond the partnership and begin offering commercial support, Pfeil said. Going forward, DataStax will be able to do just that for a commercial graph database that has greater scalability than Titan and tighter integration with Cassandra.

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Addition of new functionality, especially through acquisition, is an interesting way for a database startup like DataStax to grow, aiming for an eventual initial public offering. But it isn’t exactly an unprecedented move. The IBM-owned Cloudant database as a service last year introduced geospatial indexing and querying features. And database-as-a-service startup Orchestrate.io has sought to increase its range of capabilities, having started to build a publish-subscribe messaging component.

But in its class of NoSQL database startups with considerable funding, DataStax does appear to be more distinct now, given its acquisition of a startup with a special type of database. Basho, Couchbase, and MongoDB, among others, have embraced different expansion tactics in recent years.

The idea for Titan arose after Aurelius founder and chief executive Marko Rodriguez met Matthias Broecheler, who later became managing partner at the startup. Rodriguez, who had worked with graph databases since 2010, learned that education publisher Pearson desired “a large distributed graph database,” and the company figured it would build a layer on top of the Neo4j open source graph database to make it scale across multiple physical servers, Broecheler told VentureBeat. That’s when Broecheler told Rodriguez about his own research on distributed graph databases that could integrate with existing NoSQL technologies, Broecheler said.

Pearson liked this idea and gave the duo time to build software. And now, nearly four years later, Pearson is still a customer of Aurelius.

“A distributed graph database was something that was considered to be impossible,” Broecheler said. “Because of the connectedness of the data, people were making assumptions that you had to have it on one single physical machine.”

Then came Titan. Customers listed on Aurelius’ website include Blackboard, Cisco, Digital Reasoning, the Los Alamos National Laboratory, Palo Alto Research Center (PARC), and Shutterstock.

All eight Aurelius engineers will join DataStax, which is based in Santa Clara, California. Aurelius has always been bootstrapped; DataStax, for its part, announced a $106 million funding round in September.

The acquisition closed on Friday. Terms weren’t disclosed.