Network latency requirement for Vault with Raft

As per documentation, Vault requires lower than 8ms of network latency between Vault nodes but if that is not possible for a Vault HA cluster spanned across two zones/DCs.

What are the implications or things will need to be considered if say latency between zones is ~18ms?
Is that even recommended deployment model at all?

That’s what performance replicators are for. They extend your infrastructure and reduce latency, but it is a separate cluster - that shares your engines – all writes still end up going back to the primary cluster but reads, leases, etc all are handled locally at the PR.

Right but that is an enterprise feature, i should have mentioned that OSS is in scope here.

Then I doubt you can extend the cluster that far.

That is what I am trying to understand if latency cannot be reduced then will the cluster be operational at all? Obviously reads/writes will be impacted but what are the other internal functionalities of Vault will be impacted?