An investigation afterwards revealed that a tiny human error was the reason for the “crash”. A routine maintenance script was missing a dot when updating the Swedish Top Level Domain (TLD), causing all Swedish domains to have a wrong domain name.
Internet users normally don’t see this dot which is behind all domains, like this: “techpatio.com.” – except in this situation, the last dot went missing, so instead of “.se.” it was now “.se”, causing their system to lookup domain names as “.se.se” instead.
Even though the error was corrected within an hour, it still took up to 24 hours (in some cases it could be more) before the correction had propagated to external servers.
The mistake also meant that other domains (.com, .net etc.) with .se nameservers would be in trouble as it was not possible to look up the IP address for the domain name. Luckily that’s not usually the case, but there are some domains using .se nameservers.
Homer says: D’oh!