Which is better to use in django receiver or sessions?

Question

Django

I am creating a shopping cart for an online store and I have a choice of how to implement this shopping cart. I don’t just need to screw it up for it to work, but it’s right, because I want to put the project on my resume.

1st way is to use databases, but receivers are used in this approach, I have heard a lot that this is bad form and it is better to never use them (receivers) at all.

class Product(models.Model):
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=64, unique=True)
    description = models.TextField(default='')
    cost = models.DecimalField(default=0.00, max_digits=10, decimal_places=2)


class Cart(models.Model):
    user = models.ForeignKey(User, null=True, blank=True, on_delete='CASCADE')
    count = models.PositiveIntegerField(default=0)
    total = models.DecimalField(default=0.00, max_digits=10, decimal_places=2)
    updated = models.DateTimeField(auto_now=True)
    timestamp = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        return "User: {} has {} items in their cart. Their total is ${}".format(self.user, self.count, self.total)


class Entry(models.Model):
    product = models.ForeignKey(Product, null=True, on_delete='CASCADE')
    cart = models.ForeignKey(Cart, null=True, on_delete='CASCADE')
    quantity = models.PositiveIntegerField()

    def __str__(self):
        return "This entry contains {} {}(s).".format(self.quantity, self.product.name)


@receiver(post_save, sender=Entry)
def update_cart(sender, instance, **kwargs):
    line_cost = instance.quantity * instance.product.cost
    instance.cart.total += line_cost
    instance.cart.count += instance.quantity
    instance.cart.updated = datetime.now()

The 2nd way is to use django-sessions to store information about the user's products in sessions, the minus of this approach is that sessions live for 2 weeks, and after that the cart will be empty, which is also not very desirable.

from decimal import Decimal
from django.conf import settings
from shop.models import Product


class Cart(object):

    def __init__(self, request):
        """
        Инициализируем корзину
        """
        self.session = request.session
        cart = self.session.get(settings.CART_SESSION_ID)
        if not cart:
            # save an empty cart in the session
            cart = self.session[settings.CART_SESSION_ID] = {}
        self.cart = cart

def add(self, product, quantity=1, update_quantity=False):
    """
    Добавить продукт в корзину или обновить его количество.
    """
    product_id = str(product.id)
    if product_id not in self.cart:
        self.cart[product_id] = {'quantity': 0,
                                 'price': str(product.price)}
    if update_quantity:
        self.cart[product_id]['quantity'] = quantity
    else:
        self.cart[product_id]['quantity'] += quantity
    self.save()

def save(self):
    # Обновление сессии cart
    self.session[settings.CART_SESSION_ID] = self.cart
    # Отметить сеанс как "измененный", чтобы убедиться, что он сохранен
    self.session.modified = True

Answer 1

If you don't want to use signals, override the save method.
Well, no one bothers to use both solutions - sessions for anonymous users, a model for authorized ones.

Answer 2

You can always change the session lifetime, but the session is still tied to a specific browser, another computer, browser and that's it. And so, both options exist, there are already questions about business requirements