It depends. RxDB can be used completely serverless, while minimongo always needs a stream to the server. But minimongo is better integrated into your meteor-server-side. The approach of RxDB is to fullfill the principles of offline-first ( http://offlinefirst.org/ )

It's not quite the same thing, but I've been using the Redux store in conjunction with Mingo (https://github.com/kofrasa/mingo/) to perform sorts and filtering.