Improve inter-replica fairness for real-time APIs

[deliahu]

Description

Currently requests are assigned to replicas at random. A smarter approach would be to assign based on least recently accessed (i.e. strict ordering), smallest queue size, or something similar.

Notes

Istio's destination rules might be relevant for this, e.g. something like:

apiVersion: networking.istio.io/v1beta1
kind: DestinationRule
metadata:
  name: api-iris-classifier
spec:
  host: api-iris-classifier.default.svc.cluster.local
  trafficPolicy:
    loadBalancer:
      simple: LEAST_CONN  # or ROUND_ROBIN