I haven't seen a decent open source framework that makes it easy to package a trained model with prepocessing and postprocessing steps and deploy it behind an API.
Adding performance tracking and model validation on top of that would be great.
Then there are things like queuing/batching and autoscaling.
Closes thing that comes to mind right now is tensorflow serving and their k8s stuff (which it looks like they just renamed to tf-operator and moved to kubeflow org https://github.com/kubeflow/tf-operator)