Pulsar's geo-replication documentation has been significantly improved to cover many details that are relevant to understand when using and administering geo-replicated Pulsar clusters. It's now available at https://pulsar.apache.org/docs/4.1.x/administration-geo . There are also a lot of details about "replicated subscriptions" and why the subscription mark-delete position might not get updated to remote clusters and how the improvement https://github.com/apache/pulsar/pull/25044 available in 4.0.9 and 4.1.3 Pulsar version addresses some previous issues and what limitations remain.