run.js

function run() {
    var menu = { //...
    }

    var iceCreamChoices = new Combinator({ //...
    });
    var toppingChoices = new Combinator({ //...
    });
    var syrupChoices = new Combinator({ //...
    });

    var count = 0;
    var total = iceCreamChoices.length * toppingChoices.length * syrupChoices.length;
    var postCount = 0;
    var postCountMax = 5;

    _.each(iceCreamChoices, function (ic) {
        _.each(toppingChoices, function (tp) {
            _.each(syrupChoices, function (sy) {
                var si = setInterval(() => {
                    if (postCount < postCountMax) {
                        clearInterval(si);
                        postChoice(ic, tp, sy);
                    }
                }, 10);
            })
        })
    });

    function postChoice(ic, tp, sy) {
        ++postCount;
        db.post({
            choice: [ic, tp, sy]
        }, function (err, doc) {
            --postCount;
            done(err);
        });
    }

    function done(err) {
        if (err) {
            console.error(err);
            process.exit(1);
        }

        console.log(`stored ${++count}`);
        if (count === total) {
            console.log('done');
        }
    }
}