Mendix lets us define domain model, and later at run time it auto-generates code and database from that. I see that model usually changes with each deployment thereby forcing to change db schema. And for that we require an un-intuitive step of altering schema and adjusting the data. This becomes complicated if we skip intermediate versions when upgrading. Can Mendix start supporting MongoDB as it is a schemaless database so those customer who wish to use that as db can say good bye to such complication. The domain model will then remain at only one place, at Mendix. The added advantage is that Mongodb will bring scalability in each db operation. It is also cloud enabled and has also been exposed entirely as a service. Another newly added feature is that Mongo does most of processing in-memory. Hence real time usecases can be met by Mendix.
Our current focus is on making sure we scale well on RDBMSes. Most RDBMSes like postgres can handle quite a lot of data, more than most apps needs. Postgres specifically has been adding a lot of nosql features, like json and bson datatypes.
If you look at the market of databases, you can see RBDMSes and NoSQL databases growing towards eachother regarding features: most NoSQL databases now how a sql-like query language (apache hive, etc), and RDBMSes are adding support for schemaless datatypes.
In addition, people are learning that schemaless databases come with its own set of problems, as you need to implement the schema somewhere. Managing this in the application itself is quite complicated, as you can read here: http://developer.olery.com/blog/goodbye-mongodb-hello-postgresql/
Another interesting link, which outlines that postgres is faster than mongodb: http://www.aptuz.com/blog/is-postgres-nosql-database-better-than-mongodb/
If you have enough memory in your RBDMS server, most databases like postgres will also do their queries in memory.
Pim, would you think that the redis connector, MongoDB, and MarkLogic connectors would all look similar?
You can create a MongoDB connector and use this within your model. I created one for Redis : https://appstore.home.mendix.com/link/app/3087/Appronto/Redis-connector that is also a NoSQL database and runs in memory.
Postgres, MySQL, MSSQL or Oracle are the only supported database and is needed for the model.