The key twist in this test is that in all cases it featured a single-database-server and a single-client-server, a configuration that hardly stresses scalability or the highly-distributed nature of typical NoSQL database deployments -- or at least those of Cassandra and Couchbase. For MongoDB, it's common to see single-server deployments, according to Stirman. "Databases are often deployed on a single server, and we know that based on profiles of about 60,000 MongoDB deployments that we have access to via our cloud-management tool," said Stirman in a phone interview with InformationWeek. "When run in a distributed fashion, all of these systems are comprised of multiple, individual servers, so you have to start by looking at what a single server delivers [in terms of performance]." Contrary to this suggestion, scaled-out performance -- much less scaled-out performance across multiple data centers -- is rarely a clear multiple of single-server performance.