Agreed. I worked on a team that built out a solution like Ably described and we would run into lots of weird issues with ec2 lifecycle (often init script / conf

Agreed. I worked on a team that built out a solution like Ably described and we would run into lots of weird issues with ec2 lifecycle (often init script / configuration management issues) and deploys would take a long time (had to drain ec2 instances and bring new instances up) and there's just a lot more to manage (autoscaling groups, instance profiles, AMIs, configuration management, process management, log exfiltration, SSH keys, infra as code, etc). If you really don't want to use Kubernetes, you can get a lot of the benefits by using ECS/Fargate, but I really don't know why you wouldn't just go all-in on EKS at that point.