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An idempotent producer guarantees that single messages don't end up as duplicates in case a write is internally retried by the producer. A transactional producer allows you to write multiple messages into different partitions across multiple topics atomically. Note: if you use transactions, you automatically get idempotent writes, too.

Why I still observe duplicated data in the final output topic with "transactional producer", or with "EOS enabled streams" client?

Most likely your consumer reading from the final output topic did not have `isolation.level = "read_committed"`. This is necessary so that transactional messages can be correctly read such that not-committed data is not returned from the consumer. See below on consumer "read_committed" mode for more details.

How do I enable idempotent writes?

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