Klaviyo’s Back in Stock feature for Shopify stores has two key components: Back in Stock Flow: When someone subscribes to a restock alert, a “Subscribed to Back in Stock” event will be tracked on their Klaviyo profile. This is the event you will use to trigger your Back in Stock Flow.
https://help.klaviyo.com/hc/en-us/articles/360001895651-How-to-Install-Back-in-Stock-for-Shopify

