It would have been smarter if they hosted this on a separate reliable server altogether.
Meta has a small collection of tools on AWS to deal with large SEV0 events like these. Another one of them is a basic communication tool that does not use Meta's own servers for anything (including auth), a super basic version of the internal SEV tool.
X-Amzn-Errortype: TooManyRequestsException
X-Amzn-Requestid:
Looks like the endpoints are on aws lambda and its getting rate limited.