How can I manage fast-selling handmade products with the same SKU?

[BeccaS]

Hi!

I have products on my store that I hand make so every time I open my shop I take a certain amount of orders. There is different product listings and variants that people can choose from. I have everything under the same SKU and used an app to sync all the skus so that if one product sold, my inventory for everything would go down. Problem is, when I open shop I’m selling a bunch within seconds. I was using the app duplicate sku but I kept overselling. I talked with them and they need 1 minute processing time for the quantity to go down. Which isn’t working in this situation. Does anyone have recommendations on what to do? Another app to use? Another method of selling something that all needs to have the same sku?