https://docs.metaflow.org/api/step-decorators/kubernetes Here, I can see that I can specify custom toleration for a step. Can I also specify affinity? I need to use affinity to ensure that steps can be scheduled to a specific GPU node.

You can use node_selectors.

@kubernetes(node_selector="mylife=myrules")

It was not present in the decorator documentation, but I can see it in the source code. I will check it out.