When you update the Registration TTL for Azure Notification Hub, the old registrations that have expired based on the new TTL will not be automatically deleted. You will need to manually delete them.
To delete the expired registrations, you can use the Azure portal or the Azure Notification Hubs REST API**.**
Here are the steps to delete the expired registrations using the Azure portal.
- Go to the Access Policies tab in the Azure portal.
- Click on the policy that has the Manage permission for registrations.
- Click on the Registrations tab.
- Select the registrations that you want to delete
- Click on the Delete button.
Let me know if you have any questions or concerns on this matter.