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Except that the IP that your DNS provider resolves your apex to may be on the other side of the planet.

Fine if all you are doing is 302 to the www. Variant, but otherwise no.

This is where the Client Subnet edns extensions come in handy. This allows the DNS provider to pass along the /24 the users IP address is in.

With an extra caching key, this can even be cached.

And that also only helps if your DNS provider and the client's DNS servers also pass along that information correctly.

> "the IP that your DNS provider resolves your apex to may be on the other side of the planet"

Anycast addresses this issue, right?[1] Cloudflare uses Anycast for their IP addresses.[2]

Only if your CDN uses Anycast. Not all of them do.