Kubernetes only lets you query resources by object type and that's only a prefix range scan on etcd database. There are no indexes whatsoever in the exhaustive LIST queries, and kube-apiserver handles serialization of the objects back and forth between multiple wire types. Over the years there has been a lot of optimizations, but you don't wanna list all pods in a 5000 node high density cluster every time you spin up client-side tools like this.