concept shopping cart in category cloud
This is an excerpt from Manning's book Azure in Action.
If your roles are carrying state and you don’t want to lose that state as you completely change to a new set of servers, then rolling upgrades are for you. Or maybe you want to upgrade the instances of a specific role instead of all of the roles. For example, you might want to deploy an updated version of the website, without impacting the processing of the shopping carts that’s being performed by the backend worker roles. Remember that when doing a rolling upgrade, you can’t change the service model of the service that you’re upgrading. If you’ve changed the structure of the service configuration, the number of endpoints, or the number of roles, you’ll have to do a VIP swap instead.
Depending on the implementation of the web page, you can either allow the user to purchase the item directly or add the item to a shopping cart. In either case, the method of storing the data will be the same, so let’s look at storing items in a shopping cart.
The shopping cart can be persisted across sessions, and if the user is a registered logged-in user, you can associate this account with their user ID. Figure 14.5 represents a typical data model for a shopping cart.
In figure 14.5, the shopping cart is represented as two tables (ShoppingCart and ShoppingCartItems). The ShoppingCart table represents the shopping cart for each user, and each item in the shopping cart is stored in the ShoppingCartItems table. For each item in the cart, the ShirtId, MaterialId, and SizeId are stored, and the appropriate foreign-key relationships between tables are established.
