Apple Push Notification Service (APNS)
Today, I learned that Apple has a service that allows third party developers to send notifications to applications installed on Apple devices.
In order to use this service, developers have to generate production and staging certificates that are uploaded to a marketing service (ie: Iterable).
Iterable uploads the certificates to their cloud provider (ie: AWS), so that they can send push notifications through AmazonSNS.
These certificates have a 1-year expiration, so they have to be renewed for continuity of service.