Thanks for the response and sorry for the slow reply. I was planning on doing the custom setup, what issues might that cause?

That would mean you need to decide on who does not vote. Which brings you back to the first problem. Or having to do a custom setup on that node, and you really don't want one of your nodes to be differently configured in any way, just leads to trouble down the line.

I hope the question makes sense. Basically, I have three replica sets and I want to add one without causing an election.

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[Replica sets should always have an odd number of members. This ensures that elections will proceed smoothly](https://docs.mongodb.com/manual/tutorial/deploy-replica-set/)

[Documentation on elections](https://docs.mongodb.com/manual/core/replica-set-elections/)

[Documentation on non-voting members](https://docs.mongodb.com/manual/tutorial/configure-a-non-voting-replica-set-member/)

MongoDB documentation recommends against an even number of replicas due to problems with electing a primary. If one of these replicas is non-voting, does that solve the problem?