I've just run the test of our Pulsar Cluster on 3xVMS in 3-AZ in multi-cluster setup using Istio Ambient mode. Looks like z-tunnel and private Cilium east-west gateway is the way to go when implementing zero-trust mTLS secured networks. The result of pulsar-perf:

2026-03-03T18:28:03,875+0000 [Thread-0] INFO org.apache.pulsar.testclient.PerformanceProducer - Aggregated throughput stats --- 100021856 records sent --- 1109147.305 msg/s --- 8665.213 Mbit/s