Plan FHIR transformation of Formulary

We are a Plan looking to load our formulary to CoveragePlan and Formulary Drug. Wondering if there is a best practice out there for how to process formulary changes that occur on a monthly basis so that users don’t get multiple drugs back when calling the API. We’re thinking to use the NDC as the identifier but was wondering if other Plans have a better method. Thanks!

To clarify, you mean you only want the user to receive back records that have changed? Not fully understanding the issue you’re trying to avoid.