No, the app can manage this in most cases - if you enter buy milk twice on the same browser session, it will know how to construct the keys properly. If you buy

No, the app can manage this in most cases - if you enter buy milk twice on the same browser session, it will know how to construct the keys properly. If you buy milk once in two different sessions that are not yet consistent, in both cases you would see only one in the list and so adding another in either or both sessions will yield correct results.