Synchronous vs Asynchronous Communication

A user clicks "Place Order". Behind that click, the system has to charge the card, save the order, send a confirmation email, notify the warehouse, update the recommendation model and record analytics.

Which of those should the user sit and wait for?

Charging the card, certainly. If it fails there is no order. But nobody should stare at a spinner while a recommendation model updates.

That question, does the caller need this to finish before it can continue, is the synchronous versus asynchronous decision.