replication section should also contain an example of how to place redundant replicass across multiple nodes

this is what the replication section should say;

Replication
GSIs are not automatically replicated. They must be defined on other index service nodes for high-availability. To create a replica of a GSI, you can create the identical index definition with unique index names under 2 nodes. Queries will load balance across the indexes and if one of the indexes become unavailable, all requests are rerouted to the available remaining index. You can create more than 2 copies of the index for better redundency and load balancing.

CREATE INDEX productName_index1 ON bucket_name(productName, ProductID) WHERE type="product" USING GSI WITH

;

CREATE INDEX productName_index2 ON bucket_name(productName, ProductID) WHERE type="product" USING GSI WITH

;