It depends on how you’ve set up your cluster. In Couchbase Server 4.0 there is what is called Multi-Dimensional Scaling (MDS) in which you can scale your services independently.
For example, you could have the following 4 node configuration:
1x index node
1x query node
2x data node
In this case the three services are not evenly distributed across all four nodes allowing each service to have more dedicated resources.
It really depends on your plans for how you should determine service types and counts.
Here is a great blog post on the subject:
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