Who owns the customer?

A single person can exist as a contact in the CRM, a customer in the payment platform, a user in the application and a subscriber on an external distribution platform. Four records, four identifiers, one human.

Choose a reference, not a winner

Ownership doesn't mean one system holds everything. It means each fact has one authoritative source, and every other system stores a reference to it rather than a copy of the logic.

Practical rules

• Persist external identifiers on the canonical record from day one.
• Never match on email alone in a system where email can change.
• Decide what happens on conflict before conflict happens.