What running Kubernetes across millions of clusters taught AWS about zonal failures
Running Kubernetes across millions of clusters taught AWS that 'gray' zonal failures — where a zone is impaired but not fully down — are more dangerous than complete outages because default automated scaling converts them into regional outages. Amazon EKS applied the principle of static stability to prevent cascading terminations triggered by health checks and Auto Scaling groups, and built an automated weight-shift mechanism that moves control plane activity out of an impaired zone within two minutes.