I like the efforts here and even got a chance to contribute some patches to Rails around its recent Docker integrations. I'm also not a huge fan of Kubernetes

I like the efforts here and even got a chance to contribute some patches to Rails around its recent Docker integrations. I'm also not a huge fan of Kubernetes until you need to use it, in which case it's remarkably good at the problems it solves. The README calls this out early on but this tool's take on zero downtime is to use Traefik's built in way to queue up requests while a backend is down. That means your app will be unresponsive to users until your app has finished restarting and Traefik releases those requests. If you decide not to use Traefik then you lose this feature. It is technically zero downtime in the sense a 502 isn't served but you need to deal with timeout issues and other caveats. The end user experience is worse than Kubernetes where you can do a full rolling update where the old and new versions of the app serve traffic in real-time without holding requests. IMO these solutions can't be compared.