It’s usable in production. Not a lot of features, not audited, not a lot of tests, and not a lot of documentation and examples tho 
But other than that, there shouldn’t be problems with it. https://mops.one/rxmodb/docs
I create these libraries because I use them in my projects and hopefully someone attaches and improves them too. This one is about to be used in my next production projects. Then I’ll find more bugs if there are any.
Link to the latest thread about the DB https://forum.dfinity.org/t/rxmodb-database-v-0-1-0/21076