In my case i will index the members of a capped collection by key/id. I will then need to query a random member, then start iterating over all the following members in insert order. I can do this starting from the beginning of the collection, but i need to start from any point inside the collection. Here is a related discussion...
http://groups.google.com/group/mongodb-user/browse_thread/thread/ce5fea549a21d47c

Thank you.