devise efficient scheme for fetching multiple users versions of identical feeds

[cqr]

currently thinking that advice to publishers is to vary URL only when content varies, and vary token portion per user. That way, client can make If-None-Match: requests in sequence for a given URL but with varying tokens to ensure tokens are still valid without having to parse each of the responses.

[mahemoff]

This will help to scale the entire ecosystem, instead of treating each token-access URL as a unique feed on the basis that it might contain personalised content.