While we can be extremely proud of what we have achieved so far there was always something lurking in the dark: our primary database. From the start of Olery we’ve had a database setup that involved MySQL for crucial data (users, contracts, etc) and MongoDB for storing reviews and similar data (essentially the data we can easily retrieve in case of data loss). While this setup served us well initially we began experiencing various problems as we grew, in particular with MongoDB. Some of these problems were due to the way applications interacted with the database, some were due to the database itself.

http://developer.olery.com/blog/goodbye-mongodb-hello-postgresql/?utm_medium=twitter&utm_source=twitterfeed