[HELP] over sell/ double sell for 1 qty items AFTER payment, NO reserve/hold for 1 qty (race cond.)?

[Maomekat]

My current problem is that we sell 1 qty limited items that go on sale at a specific time eg from insta posts announcing sale of limited 1 qty item has started.

this brings a huge influx of customers at the same time. unfortunately shopify only "holds" the item after payment gateway is done, this takes few minute as for your our region we have...to use 3rd party nonshopify payment gateways(

so this results in up to sometimes 20-50 over sell items as the item is only 1 qty and the payment goes through and by that time the item is sold to someone else. so we have to manually call the other 50 customers to try to resolve some refund, gift order, reorder, apologies. it is horrible and not sustainable at all.

is there a way to use 3rd party payment gateway so that there is no over or double selling for 1 qty products in shopify? is there way to use your app or other solution for this? we don't wish to manually issue draft orders (& then use some app to deduct inventory by 1 so no other ppl can buy it or add it cart. as we want it to be an automated process done on the shopify website.

the optimal solution would be to have an app or other way which would allow us to sell 1 qty items without any double or over selling.

please help us with your expertise otherwise we might have to even move away from the shopify platform which would be very unfortunate.

Best regards,