Good point: first you're right, we do the ack on Kafka but it's not necessary. Second, this is not what I wanted to stress... and I should have not used the verb "acknowledge". What we do is upload the data on S3, then we commit partitions + positions in what we call the metastore. I can't edit my comment unfortunately.

> One downside is that you leak internals of other system (partitions).

True, but we generalized the concept of partitions for other datasources, pretty convenient to use it for distributing indexing tasks.