Once you have designed your pass, you can optionally integrate passes with your other systems and applications. You do this using the PassKit developer kit, Zapier or using the integrations available in the PassKit Portal.
This keeps your passes (the pass data) synchronised with your customer data that exists in other databases. For example, you might want to connect with CRM (customer relationship management) application with PassKit, or connect your POS (Point of Sale) software with PassKit.
You should thoroughly test your integrations to make sure that data flows between systems as you expect. Do this before distributing passes.