I’m not talking about live migration - the instance will go down and there will be a brief outage while the instance restarts on another hypervisor. The same is true of a single dyno Heroku app.
* Possibly multiple times. Instances on degraded hosts have a tendency to get stuck and you have to stop, and then stop again to force stop it, and then sometimes even that doesn't work and you have to just wait.
Source: have received lots of "EC2 Instance Retirement" emails
the topic is here is ease of use.
Comparing Heroku to VMs and correctly configured ASGs is fine for me as a sysadmin, but they’re not targeting the same simplicity.