The AppEngine Standard Java 8 API is severely limited because it is coupled to the Servlet API, which severely screwed up on the design of its async API. As a Scala developer, this limitation pretty much sinks the platform for me, since the flexible environment is really expensive and has a worse value proposition vs managed Kubernetes.
Right, but at that point, you almost might as well move up to "full" Kubernetes if you know it. I'm not saying that there's no use case for App Engine flex, just that it is kind an uncomfortable middle-ground between standard and k8s.
