When using a Kafka sink in Debezium with a materialized view, duplicate keys can cause continuous ingestion of messages into the Kafka topic.

Using distinct in the definition of the materialized view helps prevent duplicate keys from spamming the topic with the same data.

Defining primary keys in the base table can also help avoid this issue.

Adjusting the definition of the materialized view to include distinct on for the key columns can resolve the problem of continuous ingestion of messages.

Technically, using distinct on key columns like req_id and ref_id in the materialized view can be a valid solution to prevent duplicate keys from causing message spamming in the Kafka topic.