Domain queries in CQRS

Question

We are trying out CQRS. We have a validation situation where a CustomerService (domain service) needs to know whether or not a Customer exists. Customers are unique by their

Answer 1

This issues does not have to be that complex:

1. Check your reporting store for customer uniqueness before submitting the UpdateCustomer command.
2. Add a constraint to your DB for uniqueness on email address. When executing the command, handle the exception and send a notification to the user using a reply channel. (hences never firing CustomerUpdated events to the reporting store.

Use the database for what it's good for and don't get hung up on ORM limitations.