This query will be very slow
Why? Well, unless the table is not a table, and a spreading view.
If the table - read stream of data for DBMS easy way (sorting is not requested, the DBMS will choose a convenient reading order) and helmet to the requester. A simple thing, and if performance is not enough here - it is not a question to the database and its scaling, and application: why it is needed there, this is not a deterministic one million rows from a table.
A cluster is a very common word.
Master replica cold standby cluster
Master replica and hot standby cluster
N shard - cluster
Heterogeneous system with two - phase commit is still a cluster
what makes cluster
Wrong asking the question.
First determine why you a headache, for what purpose do you want to add the second server is a DBMS and why you are not the one - then see which direction you need to solve this problem to move.