Comment by felipeccastro

I use Rails and Mongo at work. There is a schema, enforced declaratively at the application layer (mongoid). With Rails Console querying the database ad hoc is even easier than with SQL, thanks to mongoid api and Ruby’s expressiveness. There are no transactions, but single document writes are atomic. Performance is pretty good; the one hardship I run into is that the mongoid api is so high level that you don’t see when you’re firing way too many queries at the dB (but that’s an ODM issue, not mongo’s, other ODMs might not do that).