Imagine we have this website.

Now let’s try to login to our account.

As we see we bought a gift card.

Now we have two requests.

1. adding a product to site.

1. Confirming the purchace.

Now let’s make a group.

now let’s change the product id to 1 which is the jacket we want to buy

Now let’s send in parallel.

after alot of trying it finally works.

The idea of the challenge is you are trying to buy a 10$ gift card the server is checking if you jave enough balance the at the checkout there is a race condition where you can checkout at the same second adding a product to the cart so that you order the product without paying for it.