@CloudNaive ,   It seems that the "Message Key Field" property doesn't work with a nested structure. This property must refer to a top level field of the record that contains the key value. In the example below I used UpdateRecord to create a top level field called "id" and update it with the value of "metadata.aggregateId". Them, on the PublishKafkaRecord I was able to use the "id" field as the Kafka message key.   Cheers, André   ... View more