70 expert Apache Cassandra users who actively use Apache Cassandra for in-production workloads. Their workloads represent more than 200 clusters running 600TB of combined data on Apache Cassandra. A few insights: * Cassandra Version 2.x (including DSE 4) is the most popular with more than 50% of deployments utilizing this version. * Performance, Tuning, and Administration accounted for 70% of total identified core Apache Cassandra challenges. * More than 30% of respondents don’t run repair over their Cassandra cluster.