I am looking for a db that runs using existing json/yaml/csv files, saves data back to those files in a directory, which I can sync using Dropbox or whatever shared storage. Now I can run this db wherever I am & run the application. Postgres feels a bit more for my needs

It feels like you want SQLite?

Why? Why would separate json/yaml/csv files be better than just... syncing using postgres itself? You point `psql` to the host you need, because clearly you have internet access even on the go, and done: you don't need to sync anything, you already have remote access to the database?