I'm really starting to like Docker now. Is it possible to have multiple independent web apps talking to one postgres and one redis installation? I have a VPS

I'm really starting to like Docker now. Is it possible to have multiple independent web apps talking to one postgres and one redis installation? I have a VPS with ~10 tiny websites, and it would be total overkill to bundle each app with its own db and caching. How would you reference that same "external" db in a fig configuration?