CouchDB has a plugin based auth system, with in built support for http / cookie / oauth, so its a matter of only allowing access to a database against an authen

CouchDB has a plugin based auth system, with in built support for http / cookie / oauth, so its a matter of only allowing access to a database against an authenticated client, it can all go over https of course. Its possible / in the plans to use on top of sqllite (and thus mysql), but it wouldnt be possible to use in the way you invisage, PouchDB + CouchDB allow you to sync data due to its data model and api, you wont be able to sync data out of your current application written with rdbms in mind and have it 'just work'