Which FHIR resource is used to define a push-based subscription from a server to another system?

• A. Observation
• B. Subscription
• C. Patient
• D. CarePlan

Answer: (B)

A push-based subscription is configured using a Subscription resource. It is specifically designed to express “interested events” from a FHIR server and how to deliver notifications to another system. The Subscription resource defines the criteria for which changes to monitor (which resources and what changes) and the delivery channel details (endpoint, payload format, and method such as rest-hook, websocket, or other notification channels). This combination enables the server to push updates automatically to a subscribing system when matching events occur.

The other resources mentioned (like Observation, Patient, and CarePlan) are data resources in the FHIR model. They may be subjects of notifications, but they do not define how or when to push those notifications.