[quote="HBSequence, post:3, topic:128198"]
My concern would be that the indices could be out of sync, at least for some amount of time.
[/quote]

There will be some lag. I can not quantify at this time, and it's dependent on your infrastructure anyway, but our aim would be with high-throughput reliable connections between the clusters that the lag would be on the order of seconds, not minutes. We are still in early stages on development of this feature, so I can only give indications of our goals here.

[quote="HBSequence, post:3, topic:128198"]
We could mitigate this by using session affinity at the network level but does xCDR have functionality to deal with this e.g. does it have immediate push updates (or is it all run on a schedule)?
[/quote]

CCR (we call it cross-cluster replication instead of XDCR = cross-datacenter replication) will operate on a pull model instead of a push model. A following index will pull from a leader index. We think this is the right model because it means that a leader index does not have to maintain state about its followers (instead, the followers maintain state about their leader). The leader maintains a sequence of operations and a marker below which it is is safe for any followers to pull. The follower pulls these operations as soon as it observes the marker advance; by default, the follower polls this marker every 500ms. Note: this is subject to change, this is only guidance on our current implementation and thinking.

Does that help?

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