User1 starts order and takes the last two units. User2 starts order 1 minute after and checks inventory. He sees 2 units left and adds them to the his order. User1 commits his order. Now User2 cannot finish his order because the products are not available anymore.
This is the problem I want to avoid. Therefore if User1 takes the product but does not finish the order I want the inventory to still show that the product is sold out to other users.