Hey @osirisx! Is it possible that those tags are also applied to the user’s profile in Shopify? Because you can make a flow that is triggered via a segment and your segment could filter in the rule: Properties about someone - Shopify Tags - Contains - production done. 

And that should populate a contact in each time they match that rule and when they do, the flow will trigger the message you set.

The only hiccup would be clean-up of that tag in Shopify so that if they order in the future, that tag is removed so that it can be re-applied to re-trigger the segment & flow again.

Hey @osirisx 

Congrats on posting your first question to the Klaviyo Community! @Spark Bridge Digital LLC Thank you for jumping in to help!

I am not a Shopify expert, but would it make sense to use the Fulfilled Order status in Shopify to mark when the order is completed? Then use the Fulfilled Order metric to trigger the flow? This would alleviate the hiccup of using a profile property to trigger the flow and allow your customers to re-enter the flow as many times as they order.