Honestly Mongodb is as good as it gets if you want to query your JSON data. Yes it might have a few challenges when it comes to scalability and disk usage but I

Honestly Mongodb is as good as it gets if you want to query your JSON data. Yes it might have a few challenges when it comes to scalability and disk usage but I don't think its anything that can't be addressed with a carefully thought out architecture. I believe Tokutek with TokuMX is addressing some of the shortcomings of Mongodb. Though I'm a bit surprised that 10gen hasn't officially commented on Tokutek's contribution. The other NoSQL solutions that would come close are CouchDB and RavenDB. I haven't tried the latter but CouchDB doesn't allow easy adhoc querying and you really have to give some thought to your Map/Reduce Views/Scripts. CouchDB is great because it also allows you to attach binary content to your JSON documents so it's great as a CMS backend but as I mentioned before, querying your data isn't as pleasant as with Mongodb. Now Mongodb does have GridFS for binary data storage but it isn't IMHO as simple to use compared to CouchDB's 'Attachments'.