Thank you @egrep. What is not clear to me, neither from the ducumentation, nor by trying out, how can I issue a view query that reads actually from the replicas? I have a bucket with index replicas on but if I shut down one of the data nodes I just get partial answers, see here: View-based primary index and node failure - it seems CB does not read actually from the replica index parts instead of unavailable active data nodes.
There is a sentence in the documentation which is not quite clear to me: “By providing replica indexes the server enables you to perform queries even in the event of node failure.” Does it mean if a node is temporarily unavailable, I can read from the replicas? (And if so, how? - automatically, or by a parameter setting like stale?) Or does it mean just simply: if I make a hard failover, the replica index becomes the active index and I can query immediately without waiting for an index to be newly built?