This document discusses the results of a NoSQL database benchmark test conducted by NHN on Cassandra, HBase and MongoDB. It describes the test environment and four test cases performed: data insertion, random reads and updates on existing data, reads only on existing data, and random reads and inserts with additional data added. The test measured average transactions per second for each database and test case. Cassandra and HBase performance varied depending on compaction levels while MongoDB update and insert performance lagged the others.