Controller calls the service.

Service returns a call to a repo with any mapping that needs to occur.

Repo calls out to database or external api and returns the promise.

Makes the work very boring and repetitive for the most part which is a good thing I think.

    function someController(req, res) {
        UserService.getUser(req.session.user)
            .then(SomeService.getSomething)
            .then((val) => res.json(val))
            .catch(handleError);
    }

    function getSomething(user) {
        return SomeRepo.getSomething(user)
            .then(MapSomething)
            .catch(alternativeHigherLevelCatch);
    }

    function getSomething(user) {
        return new Promise((resolve, reject) => {
            database.getSomething(
                'defined parameters',
                user,
                resolve,
                reject
            )
        });
    }