Initial add to cart action takes 10+ sec, the following are almost instant for a while

Add to cart action takes over 10 seconds, however if we go ahead and add the same product to the cart it is much faster for some time. We assume it is due to browser cache TTL setting (4h in our case). We tried disabling Brotli compression as well as all query string caching. The issue is present on pretty much all of our woocommerce stores. I hope we can resolve this issue together and thank you for your help.

Example, where the issue is found (add to cart actions on and )

Hello there,

I hope you are fine. I’ve got the same issue.

Did you manage to find the cause and a solution ?