I am increasingly convinced that those who blame MongoDB for any kind of data corruption are waving hands out of desperation. Every single time I had an issue with data I ended up finding code that I’ve written or code that was written in a library that I used. The hardest bugs involve some kind of concurrent operation, including one I’ve described in a new post on the Artsy Engineering blog: Data Corruption and Concurrent Updates to Embedded Objects w/ MongoDB. Read it, especially if you are using an ODM to manipulate embedded objects.
I also want to point out two magical lines of code that I use all the time.
Knowing what Mongoid is doing is half the battle.