Hello @bgkim    Thanks for using Cloudera Community. To your Q, the Composite Primary Key would require using both A & B in WHERE Clause as the Indexing is done collectively. As such, Your SELECT Query would ideally benefit upon creating a Local Index on A & C. You may review [1] as Read-Heavy Use-Case benefit via Global Index with Penalty incurred during Writes. Additionally, Phoenix offers Covered Index & Explain Plan helps confirming the Index Usage. Link [2] offers few examples as well.    With all recommendations, Best Advise is always to review the Performance internally prior to implementing them in Production.    Regards, Smarak   [1] https://phoenix.apache.org/secondary_indexing.html  [2] https://learn.microsoft.com/en-us/azure/hdinsight/hbase/apache-hbase-phoenix-performance  ... View more