You don;t need ot use Redis Cluster, but for bigger deployments, you will need to if you want HA.
To set up Redis Cluster with a set of Tyk Nodes, you just add the hosts to the
hosts field in the tyk.conf (and all the other components have a similar setting). You need to also set the
enable_cluster field to true under the redis settings.
The Tyk nodes themselves don;t need to be clustered in any way, they just need to be able to each see every redis node so they can distribute read/wriotes and find the right shard for keys.