• Written in: Java
• Main point: Best of BigTable and Dynamo
• License: Apache
• Protocol: Thrift & custom binary CQL3
• Tunable trade-offs for distribution and replication (N, R, W)
• Querying by column, range of keys (Requires indices on anything that you want to search on)
• BigTable-like features: columns, column families
• Can be used as a distributed hash-table, with an “SQL-like” language, CQL (but no JOIN!)
• Data can have expiration (set on INSERT)
• Writes can be much faster than reads (when reads are disk-bound)
• Map/reduce possible with Apache Hadoop
• All nodes are similar, as opposed to Hadoop/HBase
• Very good and reliable cross-datacenter replication

Best used: When you write more than you read (logging). If every component of the system must be in Java. (“No one gets fired for choosing Apache’s stuff.”)

For example: Banking, financial industry (though not necessarily for financial transactions, but these industries are much bigger than that.) Writes are faster than reads, so one natural niche is data analysis.