Web applications nowadays have huge demand for data processing, and they need to get them, process them, and displayed them fast. Traditional relational tables and big SQL engines fail to serve that purpose. NoSQL movement is on the rise. There are huge numbers of alternatives to SQL like BigTable, HBase, CouchDB, Cassandra and MongoDB. They are all fast but you'll need to implement new way to work with them, since all of them have they own query languages. It would be nice that we can use them in similar or same way in our projects, after all ORM layer is there for that to decouple our objects from underlying storage. MongoDB is one of most popular NoSQL solutions and easiest one to install. For HBase i would had to install cygwin or virtual linux, and still will be hard to confgiure it right. MongoDb is easy, it plays out of the box, just unzip it, and it still offers some nice features like MapReduce, Replication and Sharding. Datanucleus is one of the leading ORM provid...
Sasa Jovancic, private blog