Hi @JulienLdt,
Thanks for asking this great question in the Community!
As Klaviyo doesn’t have in-house metrics for subscription-based actions, it is a great idea to build this out via API! Whenever you are using Segments, it’s important to remember that you can only dynamically pull information into segments that Klaviyo is able to identify or has stored in your account. While you could create Lists via API that hold customers who have created a subscription for a certain product, there is an easier way to track Server-Side Metrics in Klaviyo such as ‘Started Subscription’, ‘Updated Subscription’, and ‘Cancelled Subscription’ that can all be installed via API, explained and prepared for users in our Help Center Documentation.
This would be an easier way to create the data for the metrics you wish to segment. I would also suggest creating product-specific tags or names in the event data you install so you can further segment the data to filter the events based on each product.
When you have installed the data to create these subscription event metrics, I would recommend Creating Metric-Triggered Flows after each of these possible events to further personalize the customer journey!
Finally, check out another conversation a user in the Community was having about a similar subscription question!
Best,
Taylor