Inventory reduction problem

JEET mentioned that there are three ways to deduct inventory with an ecommerce site. These were at the cart, at payment, and when shipped. At payment was said to have a problem with two people having the possibility of ordering the same last item in their carts.

Now, to me it seems that all three would have this possible problem and therefore a lock would need to be used.

May I have an explanation please?

Thank you,
Joshua...

Inventory reduction problem

from Databases https://ift.tt/3exN1kd
via IFTTT