Read-only nodes are replicas of a cluster’s primary node located in additional geographical regions. Using read-only nodes reduces latency for users connecting from those regions.
Communication between primary and read-only nodes is SSL-encrypted and sent over the public network.
To add a read-only node, click on the name of the cluster to go to its Overview. At the bottom of the page, click the Add a read-only node link to go to the read-only node creation page.
Select the size, which must be equal to or larger than the primary node, then select the datacenter and name the node. When you’re done, click Create a read-only node to provision the node.
Like primary nodes, you can limit access to a read-only nodes to trusted sources and access read-only nodes using a command-line client and the connection string in the node’s Overview page.