For 2.6, index intersection does not apply when the sort( ) operation requires an index completely separate from the query predicate. Do you have any plan to support index intersection for both query and sort in the future. Currently our query criteria are different from sort field, we have to create lots of compound indexes, which uses lots of memory. It would be nice if we only need to create single field indexes and let Mongo to choose them for both query and sort. It is ok to use hint to tell Mongo which index for query and which index for sort.