Creating custom Object ID in MongoDB

Question

I am creating a service for which I will use MongoDB as a storage backend. The service will produce a hash of the user input and then see if that same hash (+ input) already

Answer 1

I just found out an answer to one of my questions, regarding indexing performance:

If the _id's are in a somewhat well defined order, on inserts the entire b-tree for the _id index need not be loaded. BSON ObjectIds have this property.

Source: http://www.mongodb.org/display/DOCS/Optimizing+Object+IDs