[ceph-users] Indexless bucket constraints of ceph-rgw

I am considering Indexless bucket to increase the small file performance and maximum number of files using just HDDs. When I checked the constraints of indexless bucket in ceph-docs, it indicates the possible for bucket list problem, so I just know it makes the problem of versioning and sync. I don't understand what means of it. and I just guessed it's similar with db index feature. but it's not. Could you tell me the indexless bucket constraints?