We have Sales Cloud as our database of record and contacts flow through from Sales Cloud to Marketing Cloud. Our contact key is currently the 18 digit contact/lead key from CRM.
We have a new use case where we want to initiate an abandoned cart journey when a user reaches a specific step in the e-commerce platform. Our E-Comm platform will make an API call to trigger the journey in Marketing Cloud but the contact may or may not be part of our CRM at that point in time. The contact will be created in our CRM once they make a purchase but in this case they may just be browsing the site and left items in their carts.
Looking for guidance on what we should use as the contact key when triggering the Abandoned cart journey knowing that the email is what is captured on the e-commerce site but eventually that same person can be a contact in CRM with an 18 digit id once they purchase. I want to make sure I handle consent appropriately if they unsubscribe from the abandoned cart email. Will I be able to merge both Contact records in Marketing Cloud ? What's the best practice.