UNION query with Use keys


I’d like to retrieve documents from two unrelated buckets, are there any performance gains from using a Union instead of two queries?

select x from bucket.collection USE KEYS = "xyz"
select y from bucket2.collection2 USE KEYS = "abc"

I remember with CB4, getting the document directly by key would call the data server directly instead of calling the query server, does USE KEYS have the same gains in the latest CB7+ ?

From Client to server 1 query vs 2 queries (2 round trips)
With in the server not much difference.

As you already know the keys you can use KV collection get from SDK avoid 2 hops. You can gain couple of ms