Ok, so if I move the database stuff to the host app how will it work?

Here is an example of what one of the current routes does in SugarTown
(remember its just a CRUD app):

Post[Route.Root().AnyIntAtLeastOnce("id")] = parameters =>
        {
             var model = DocumentSession.Load<Post>((int)parameters.id);
             this.BindTo(model);
             DocumentSession.SaveChanges();
             return Response.AsRedirect("/posts");
        };

If I move the data storage out how to the host app I'll still need some generic interface to tell it to save the data so IDocumentSession becomes IDatabase?