For the final time - on our side it worked correctly. It was locked. Nobody new could order or get to the PayPal. They were ALREADY AT PAYPAL. PayPal link had a LIMIT OF 1 STOCK. PayPal allowed 16 to

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It's fine if you don't want to reply again, but seriously actually read what we are saying.

Moving the goalpost, the problem is why they get to paypal link in the first place, if your "multi-step limits and checks" working, they won't touch the paypal link in the first plac

Agree! You reserve all the rights to own RDP services & REDEEMING.

Again, and this will be my last reply to this - we have a lot of work to tackle today....

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We have 3 teller, each will check the vault to tell customer its has gold in it before taking order, but to get to vault it need 1 minutes go and 1 minute back to check the gold

Yeah, databases were invented to handle concurrent events in consistent ways.

We locked it the second first one clicked the PayPal button. But they all clicked at the exact same time. Same hour, minute, second. Only ms differences.

It's perfectly possible to make atomic locks using the filesystem (although there are significantly better approaches). As a hint, e.g. create a symlink from "/tmp/stupid-way-of-doing-locking

Read my last reply. We did indeed lockfile it. But everyone was on PayPal, not on our website. Our website page was locked. Anyone new coming to it got an out of stock. Those already at PayPal our sys

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why manage inventory based on whether paypal makes a payment instead of orders?

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When the first person clicked the PayPal button, a lockfile was made. The page would have loaded out of stock at that point. If IPN came, lockfile became permanent. If not in 5 minutes, it unlocked.

You are naive, paypal job is to handle payment, not checking your stock

Dartnode style queue is the best way. Have one db table (handles concurrency) which gives out reservation token and notes the position, wait for payment, release after some time, repeat. Refunding doz

You didn't read what I wrote. Don't send two customers to paypal and hope that paypal will decide who was first. Decide YOURSELF who was first, and send that person to paypal. If they don't complete t

Incorrect. They were on payment page at same time. Race condition wasn't possible to correct with 2ms differences.