// +optional
  optional bool ready = 1;

  // serving is identical to ready except that it is set regardless of the
  // terminating state of endpoints. This condition should be set to true for
  // a ready endpoint that is terminating. If nil, consumers should defer to
  // the ready condition.
  // +optional
  optional bool serving = 2;

  // terminating indicates that this endpoint is terminating. A nil value

  optional string kind = 1;

  // Namespace of the referent.
  // More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/namespaces/
  // +optional
  optional string namespace = 2;

  // Name of the referent.
  // More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#names
  // +optional
  optional string name = 3;

  // UID of the referent.

  optional string kind = 1;

  // name is the name of the referent; More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#names
  optional string name = 2;

  // apiVersion is the API version of the referent
  // +optional
  optional string apiVersion = 3;
}

  optional string kind = 1;

  // Name of the referent; More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#names
  optional string name = 2;

  // API version of the referent
  // +optional
  optional string apiVersion = 3;
}

  optional string kind = 1;

  // Name of the referent.
  // More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/names#names
  optional string name = 3;

  // UID of the referent.
  // More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/names#uids
  optional string uid = 4;

  // If true, this reference points to the managing controller.
  // +optional

//
// Kubelets use this API to obtain:
//  1. client certificates to authenticate to kube-apiserver (with the "kubernetes.io/kube-apiserver-client-kubelet" signerName).
//  2. serving certificates for TLS endpoints kube-apiserver can connect to securely (with the "kubernetes.io/kubelet-serving" signerName).
//
// This API can be used to request client certificates to authenticate to kube-apiserver
// (with the "kubernetes.io/kube-apiserver-client" signerName),

Along with caching, partial computations are a critical performance optimization to ensure that we do not need to build (or send) every resource to every proxy on every change. This is discussed more in the Config Serving section.

### Config Serving

Config serving is the layer that actually accepts proxy clients, connected over bidirectional gRPC streams, and serve them the required configuration.

   while also keeping file watchers on them. Envoy proxy then connects to istio-agent's SDS Server through the defined socket path and gets the cryptographic...

  // A label query over pods that are managed by the daemon set.
  // Must match in order to be controlled.
  // If empty, defaulted to labels on Pod template.
  // More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#label-selectors
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.LabelSelector selector = 1;

  // An object that describes the pod that will be created.

  // A label query over pods that are managed by the daemon set.
  // Must match in order to be controlled.
  // It must match the pod template's labels.
  // More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#label-selectors
  optional k8s.io.apimachinery.pkg.apis.meta.v1.LabelSelector selector = 1;

  // An object that describes the pod that will be created.