Shopping cart interaction how should the user check out?

1. What happens if two users add the same product to their cart?
2. Does add to cart mean buying?
3. What will get displayed on the second navigation bar when the user clicks on the Add to cart button of a product on the products page?

What happens if two users add the same product to their cart?

While adding to the cart, you cannot determine whether any other user has added it or not, if the time is same. While placing the order, your query will allow only one transaction and after the completion of that it will process another request. So, when both request will hit the database, one will go through first.

Does add to cart mean buying?

The add-to-cart button is a feature of ecommerce stores that allows customers to choose items to purchase without actually completing the payment. For online stores, it lives on individual product pages, functioning as the digital equivalent of a shopping cart in a brick and mortar store.

What will get displayed on the second navigation bar when the user clicks on the Add to cart button of a product on the products page?

The AppBar includes a shopping cart icon with a badge that updates the item count whenever a user presses the Add to Cart button. The second screen, the shopping cart screen, displays a list of the things that the user added to it.