RSS feeds and JSON APIs don't provide the capabilities of Mirroring Support that XML-RPC does

[boitavoi]

What's the problem this feature will solve?

Hello there
I'm trying to query PyPi's registry for changes, meaning using the existing APIs to get information about the changes that happen in the registry once in a while. Changes like package addition/deletion and new releases of existing packages

After going through PyPi's APIs the only way I managed to achieve that goal is by using the "Mirroring Support" methods of the XML-RPC API: changelog(since, with_ids=False), changelog_last_serial(), changelog_since_serial(since_serial), list_packages_with_serial(). These functions allow me to retrieve registry information relative to a specific timestamp or serial id of a registry update.
However, PyPi's XML-RPC docs page (https://warehouse.pypa.io/api-reference/xml-rpc.html) states that the XML-RPC API is scheduled to be deprecated in the future and advices users to migrate to the new APIs (RSS and JSON)
After looking into those APIs I couldn't find a way to replicate the functionality that XML-RPC provides (as I described earlier).
Describe the solution you'd like

I would like to know if I'm missing something here about the functionality of the new APIs - RSS feeds and JSON APIs, meaning there is a way to achieve this functionality. If not, I would like know if there is a possibility that these features will be added to the new APIs, as I don't want to depend on an API that might drop in the near future.
Additional context
Thanks in advance :)

[di]

You're not missing anything: it's not currently possible. Some prior discussion of related issues in #284, #347, #2551, and #7116.

I think we can probably close this issue in favor of those.

[cooperlees]

@dstufft: This sounds like another use case for extending the Simple API to have a changed since serial call / date or what ever it was you have in mind. Should we start a PEP for that idea or does it need one? I get mine emotions when we propose packaging PEPs.