I am researching rolling out multiple clusters and using Cross Cluster Search when needed. However, there are a few open question that don't seem to be addressed in the official documentation yet.
- How should upgrades be handled?
- Can a 5.x cluster talk to a 6.x cluster or is the reverse true?
- Are there any practical limits to the number of remote clusters that can be connected to? (10, 100, 1000?)
- Are there any practical limits to the number of shards that can be queried in a single request?
Cross cluster search looks promising but I want to make sure that we have reasonable upgrade plans in place and practical performance expectations.