I'm planning to migrate the APNs to the Authentication tokens system from the old (certificate based), but I don't want to invalidate the existing valid tokens. Does anybody have any experience with this? Will the existing token still works after migration?
TIA
It's important to separate the notions of device tokens and authentication tokens (also sometimes called "provider tokens" in the APNs docs).
Device tokens are analogous to a phone number and are used to address a notification to a specific app running on a specific device. Device tokens are unique to a specific app/device/environment (production or sandbox) combination, but don't change as a function of your authentication strategy.
Authentication tokens are completely distinct from device tokens, and are created by the sender using a private key issued by Apple. Authentication tokens have a short lifetime (an hour), and can be used to authenticate requests to send notifications to multiple devices. You can think of authentication tokens as short-lived API keys for sending notifications to all of the "topics" that you own.
That said, changing from certificate-based authentication to token-based authentication will have no effect on your existing device tokens. Everything will continue to work just fine.
