We currently have no plans for read-only nodes. Something we’re considering for
the future is to allow reads from nodes which are not the leaseholder
(“follower reads”), which is tentatively slated for our 2.1 release in October.
With respect to your question, the cluster doesn’t need consensus to serve a
read, but without follower reads, reads cannot be served from any node which is
not the leaseholder. This means that as the replication factor goes up, there
shouldn’t be any impact on read latency due to consensus, but there also won’t
be any real benefit in terms of throughput or latency to increasing your
replication factor in this way. Writes, however, do need to go through
consensus, and so your write latency will be affected.
Does this answer your question?