On Tuesday, Rackspace (RAX) announced that is has acquired "MongoDB" database-as-a-service provider ObjectRocket, saying the purchase will expand its ability to "help customers shoulder big data in the cloud for today's most demanding applications."

MongoDB is a popular "NoSQL" database management system, and Rackspace cites research from The 451 Group saying that revenue from NoSQL software is expected to grow at a compound annual rate of 82% through 2015. For context, Wall Street analysts expect Rackspace's own earning to grow at about 30% -- a very respectable rate, but nowhere near the lightning speed of this new on-demand software business. By taking ownership of ObjectRocket's "best-in-class" platform for NoSQL, Rackspace hopes to participate in this growth.

Financial terms of the acquisition, however, were not disclosed. Nor were Rackspace's own expectations for how the purchase would affect its business going forward. Rackspace shares sat out most of today's rally, gaining only 0.1% to close at $55.12.