Another problem is that some of our services might not need to know about the whole Customer resource, and by insisting that they go look it up we are potentially increasing coupling. It could be argued, for example, that our email service should be more dumb, and that we should just send it the email address and name of the customer. There isn’t a hard-and-fast rule here, but be very wary of passing around data in requests when you don’t know its freshness.
