Kafka tombstones via console producer
Key + null value = tombstone. Use null.marker so the CLI can send it.
bin/kafka-console-producer.sh --bootstrap-server localhost:9092 \
--topic my-compacted-topic \
--property parse.key=true \
--property key.separator=: \
--property null.marker=NULL
# Then type: user123:NULL
Compacted topics need a null value to delete a key. The console producer’s null.marker makes that one line instead of a custom producer.