Inspired by this question ( soon to be closed or shunted off to obscurity )
I wondered how hard really would it to do this?
Of course, there are counter arguments why it's a complete waste of time
Anyway, as I mentioned in the above SO answer, it's a simple wire protocol that uses a request/response so it should be straight forward enough to implement. Data is encapsulated using a BSON format which is a binary JSON format. We don't yet have a BSON parser but @rebolek had one in 2013 and is working now to finish and release it.
So, this stub is here for someone who wants to work on it.
MongoDB wire protocol documentation
Free online MongoDB server - not sure how useful this is going to be since it uses https, and we do have some current problems with supported cipher_suites, and also they use http redirects which we can manage but it's a pain.
a CRUD implementation in Prolog