Last week I spent in Munich, Germany attending and speaking at DrupalCon. This was my first DrupalCon, and I have to say I was amazed with both the size (1800+ people) as well as the great community they have built. My main reason for going was to see how Drupal and MongoDB work together, and what we can do to make their integration better.
From my side, MongoDB related events were me presenting at the Munich MongoDB Usergroup on Indexing on Tuesday evening, a birds of a feather session on Wednesday, where I showed how Drupal 7 can be used with MongoDB at the moment and my presentation "Introduction to MongoDB" where I outlined what makes MongoDB such a good fit for Drupal. The presentation on the conference were standing room only.
I have taken quite a few things back from this conference. First of all, it seems clear that there is a lot of interest in the Drupal community to have MongoDB working as a first-class citizen, especially for higher traffic sites. Right now, there is a module that "just" integrates into only a few places in Drupal. We also support the EntityFieldQuery module.
But, as most of Drupal 7 is using hard coded SQL queries, it is hard (though possible) to run everything with MongoDB instead of MySQL. Due to the inherent design issues with Drupal 7 it is not easy to use and this then results that sites such as the WhiteHouse's petition website moving back from MongoDB to MySQL. In their own words:
"The current release depends on MongoDB. When we first created the application, we wanted to make sure we had a highly scalable application and database to meet our anticipated performance needs under high loads. We have been running MongoDB in production for over a year, but we have decided that the performance benefits it provides are outweighed by the complexity of trying to extend Drupal features backed by MongoDB."
Of course, we would like MongoDB to be used with Drupal and we are putting effort into making this a lot better for Drupal 8. Besides more interaction with the Drupal community such as sponsoring and attending DrupalCon, we also financially support Károly Négyesi (or chx as most people know him) to make sure that Drupal 8 will work a lot better with MongoDB. Nevertheless, there is still a lot of work to be done there.