The approach of using "an offset + a limit to partitions" cannot guarantee the correct coverage of the indexation

Ok, thanks for the explanation. The concurrent insertion issue could probably be worked around with a final, "no-limit" partition, but the concurrent deletion would indeed be problematic.
We may still have similar issues with the approach "one ID interval per partition", most notably with concurrent deletions, but at least those issues do not present the risk of "cascading" to other, unmodified elements.

Anyway... I'm out of ideas. Let's just document the limitation (if it hasn't been documented already).

Also, about maxResults: agreed, a bit of documentation is required. In particular, it seems the limit is applied per entity (e.g. with maxResults=100 and 2 entities, you could end up indexing 200 entities), and that should be clear from the documentation.