I want to write the URLconf for a shopping cart app I wrote in django. I wonder what is the preferred way of constructing URLs.

The URL is accessible by the users via a hyperlink(They are not supposed to type it in the address bar). It adds the specified item to their shopping cart. should I

use the pk for the item:

```
http://example.com/add/253

```

or use a unique slug:

```
http://example.com/add/unique_item_slug

```

Do any of these approaches have security or performance advantage. Is there any reason to prefer one?