Fixed an issue that blocked Kafka 4.x features after upgrade

If you upgraded an Aiven for Apache Kafka® service from Kafka 3.x to 4.x, stale broker or controller registrations could prevent metadata.version from being finalized. This could block access to Kafka 4.x features even after the upgrade completed.

To resolve the issue, apply the Unblock the finalization of Apache Kafka 4.x upgrade for clusters with stale controller registrations update, available from your service's maintenance updates. After the update is applied, contact Aiven support to finalize the Kafka 4.x upgrade. Aiven support removes any confirmed stale broker and controller registrations and finalizes metadata.version on your cluster. No additional restart or node recycle is required after the maintenance update.

The root cause is an unresolved upstream Apache Kafka issue, KAFKA-20295.