[waz0wski]

the last big us-east-1 outage was ... DNS - and it's usually DNS or software-defined core networking causing these cascading failures

Loss of DNS causes inter-service api calls to fail, then IAM and all other services fail. Anything not built to handle those situations with backoff causes a 'stampeding herd' of failure/retry and exacerbate the outage

Review the AWS statements about outages here - https://aws.amazon.com/premiumsupport/technology/pes/