When the configuration of a REST endpoint has a property of type reverseReference, queries asking for that field will make rest2ldap search for all entries having the same attribute value as the entry passed as parameter.
The search could translate very quickly in an unindexed search, as explained in
In cases where the attribute is multi-valued , moreover, there will be as many searches issued as there are values, possibly all of them non indexed.
To avoid evaluating all the searches over the entire backend, it would be nice, when possible, to use an OR filter with all the values, to get all entries at once.
A related problem is also that such searches may encounter server limits (search or cursor limits), therefore they should be allowed to proceed regardless.