Looks like a DNSSEC issue, not a nameserver outage. Validating resolvers SERVFAIL on every .de name with EDE:
RRSIG with malformed signature found for
a0d5d1p51kijsevll74k523htmq406bk.de/nsec3 (keytag=33834)
dig +cd amazon.de @8.8.8.8 works, dig amazon.de @a.nic.de works. Zone data is intact, DENIC just published an RRSIG over an NSEC3 record that doesn't validate against ZSK 33834. Every validating resolver therefore refuses to answer.
Intermittency fits anycast: some [a-n].nic.de instances still serve the previous (good) signatures, so retries occasionally land on a healthy auth. Per DENIC's FAQ the .de ZSK rotates every 5 weeks via pre-publish, so this smells like a botched rollover.
RRSIG with malformed signature found for a0d5d1p51kijsevll74k523htmq406bk.de/nsec3 (keytag=33834) dig +cd amazon.de @8.8.8.8 works, dig amazon.de @a.nic.de works. Zone data is intact, DENIC just published an RRSIG over an NSEC3 record that doesn't validate against ZSK 33834. Every validating resolver therefore refuses to answer.
Intermittency fits anycast: some [a-n].nic.de instances still serve the previous (good) signatures, so retries occasionally land on a healthy auth. Per DENIC's FAQ the .de ZSK rotates every 5 weeks via pre-publish, so this smells like a botched rollover.