While reading info about the Kafka Indexing Service (for banner impression data) I noticed that all the Druid 0.12.x releases contain improvements and fixes for the extension. They also offer a lot of new interesting things, like the built in caffeine cache extension, improvements in security auth (kerberos and basic auth), SQL query performance, etc.. It would be great to upgrade the Analytics Druid cluster before starting any work with KIS in my opinion, especially since the upgrade procedure when a KIS is active is more elaborate.
This restriction is now fine since we are running 0.11:
Please note that after upgrading to 0.12.0, it is no longer possible to downgrade to a version older than 0.11.0, due to changes made in #4762. It is still possible to roll back to version 0.11.0.