One critical feature for a PaaS that you’re going to run your business on is limiting the number of service outages while upgrading. CoreOS is a good start in that the enterprise toolchain allows the operators to control the rolling reboots, however, looking at the deis instructions for upgrading requires that the entire PaaS fabric is disabled during the upgrade. Before going all “in place” vs “migration” you need to understand that both are just as volatile and the chances that there is going to be an outage is very high.The only way to manage the potential service interruption is to own the service and the integration points so that the single point of failure between micro-releases is managed.Green/Blue deployments applies ALL aspects of the stack. The OS, the PaaS and the application/micro-services.UPDATE: deis.io now supports in-place updates. I need to give this a try.