We use Fastly (and our site is down too) but I asked them about this a couple of years ago. It is deliberate. They said it was so they can tell if it is their Varnish service or the customer's Varnish service that is down

Fastly modified the Varnish error to ensure that it is known if the error is returned by Fastly's Varnish or by the origin's Varnish should the customer run their own Varnish on the origin.

Looks like an error (typo) with Varnish .. it's the same on multiple sites.

Maybe a good way to work out which versions are being used.

Mediation is a real word though?

This seems like it's intentional given the context.

I don't see the typo? definitely a fastly problem though..

Fastly error: unknown domain: numpy.org.

Details: cache-pdk17841-PDK

I assumed it was an intentional pun.