With Campaign Classic we would like to send a special offer email to the customer who visits some products in the website. But we do not want to send the email every customer on every product, we will have a business logic like if the product's price is higher than $100 and user is a VIP user etc. As I see, transactional messaging does not allow to run business rules like above. Is this approach can be done with workflows? I can trigger the workflow via api when a customer visits the product's page and then some business logic happens, if user and product is eligible for special offer then email is sent. Is this approach is fine with performance aspect? Should my workflow run always in order to accept external signal?
It's more efficient to batch the work. An external signal can be used instead of a scheduler, though requests should still be captured outside the workflow and staged in a table, for reliability and auditability. Calls to the signal can be made by a custom endpoint as a single user-facing api; or users can call 2 ootb api's, one to write the request and one to have the workflow pick it up.