[joyinsky]

Does any functional example of this architecture exists?

[programminggeek]

Yep, there is an example twitter clone called Status. https://github.com/RetroMocha/obvious_status

It can run as a rails app, sinatra web app, sinatra api app, command line app, or desktop app using jruby. Backend database is pluggable and can use json files, mongo, mysql, or even its own api as a data source without switching the application code itself.