I've a customer master system that's used for storing, updating and retrieving customer information. The service calls is of the order of 300-600 milliseconds. Obviously it's the system of records.
I'm designing another promotional system that would need customer master information. I'm wondering if the promotional system should make calls to customer master system every time it needs customer master information or should it keep a copy of database and try to synch up with the customer master system periodically?