How to find out all customers who bought a particular variant(sku)? I am using asp.net identity for users. Any databse insight would be very helpful.
Have a look at this page, example 5, it might give you a hint how to achieve that. When you have the orders, you can get the users from them
A little bird tells me that the Profile Store will very soon be able to support you on this one too. So if you are using the Profile Store, perhaps keep an eye on some of the news that is coming out of the (currently running) Ascend 2019 Global conference ;-)