# The FHIR Subscription lifecycle with AWS HealthLake
<a name="managing-fhir-subscriptions-lifecycle"></a>

Follow these steps to understand the FHIR Subscription lifecycle:

1. Create a `SubscriptionTopic`
   + Create a `SubscriptionTopic` with status `"unknown"`

1. Create a `Subscription`
   + Create a `Subscription` with status `"requested"`
   + HealthLake validates the `Subscription` configuration
   + `Subscription` *must* reference an already existing topic (topic *must* be in status `unknown`, `draft`, `active`).

1. Activation
   + If valid, HealthLake updates status of `Subscription` to `"active"` 
   + While creating a `Subscription`, if the topic given was in status `"unknown"`, HealthLake updates the status to `"active"` once the Subscription is also active 
   + Subscriptions usually take 5-10 minutes to create successfully
   + If `Subscription` does not create successfully, the status will change to `error` where you should perform a DELETE operation, then retry creation of a Subscription. You can view the `"error"` field in the Subscription resource to see why the Subscription did not create successfully.

1. Ingesting while Subscription is `active`

1. While `Subscription` is `active`
   + HealthLake monitors for events matching your criteria
   + Notifications are sent to configured endpoint when matches occur

1. Error Handling
   + HealthLake attempts retries for 14 days and then stops retrying for those events

1. Deactivation
   + A `Subscription` can be deactivated by:

     Setting an end date (automatic deactivation)

     ```
     {
       "resourceType": "Subscription",
       "meta": {
         "profile": [
           "http://hl7.org/fhir/uv/subscriptions-backport/StructureDefinition/backport-subscription"
         ]
       },
       "status": "requested",
       "end": "2026-07-31T05:38:17.2404292+00:00",
       "reason": "Test subscription for walkthrough",
       "criteria": "https://healthlake.<AWS_REGION>.amazonaws.com/datastore/<datastoreId>/r4/SubscriptionTopic/<your topic id>",
       "_criteria": {
         "extension": [
           {
             "url": "http://hl7.org/fhir/uv/subscriptions-backport/StructureDefinition/backport-filter-criteria",
             "valueString": "Encounter?subject=Patient/<patient id>"
           }
         ]
       },
       "channel": {
         "type": "event-bridge",
         "endpoint": "<your event bus arn>",
         "payload": "application/fhir+json",
         "_payload": {
           "extension": [
             {
               "url": "http://hl7.org/fhir/uv/subscriptions-backport/StructureDefinition/backport-payload-content",
               "valueCode": "id-only"
             }
           ]
         }
       }
     }
     ```

     Deleting the `Subscription` resource

     ```
     DELETE https://<baseHealthLakeURL>/Subscription/<your subscription resource id>
     ```