I am trying to get this working with mysql but am getting stuck with: org.skife.jdbi.v2.exceptions.UnableToObtainConnectionException: java.sql.SQLException: Cannot create PoolableConnectionFactory (Unknown system variable 'query_cache_size'). We are using mysql 8.0.42, druid 34, and mysqlconnector 9.4

This could be related to the version of mysql we are using here. From guide: The MySQL extension uses Oracle's MySQL JDBC driver. The current version of Druid uses version 8.2.0. Other versions may not work with this extension. https://druid.apache.org/docs/latest/development/extensions-core/mysql/#install-mysql-connectorj