The document discusses benchmarking the performance of various NoSQL databases including Cassandra, HBase, MongoDB, MySQL Cluster, MySQL Sharded, and Riak. It describes using the Yahoo! Cloud Serving Benchmark (YCSB) tool to evaluate the databases under different workloads on an Amazon EC2 cluster. The results show that HBase has the best performance for write-heavy loads during data loading, while MongoDB and MySQL Sharded perform best for read-heavy workloads due to their caching mechanisms.