Implement FHIR R5 topic-based Subscriptions with the R4 backport (subscriptions-backport IG) using a REST-hook channel

In-depth guide

Steps

1. Confirm the server supports the subscriptions-backport IG by checking for the backport-subscription profile in the CapabilityStatement or SMART configuration
2. Create a Subscription resource with the backport profile; set channel.type to rest-hook, channel.endpoint to your HTTPS callback URL, and channel.payload to application/fhir+json
3. Set the criteria element using a topic-based reference: criteria = the canonical URL of the SubscriptionTopic that represents the event of interest (e.g., a patient-admission topic URL)
4. POST the Subscription to [base]/Subscription; expect a 201 Created response with the created Subscription including a server-assigned id
5. When an event matching the topic occurs, the server POSTs a notification Bundle to your endpoint; respond with 2xx within the server's timeout to acknowledge
6. Parse the notification Bundle: type=subscription-notification, the first entry is a SubscriptionStatus resource describing the event count and the Subscription reference; subsequent entries are the focus resources if full-resource payload is configured