We used it for a few months now, it works. we have 3 datacenters with ~10ms of delay between them and no problems.
Over WAN will work, but not sure how reliable will be. Regards.
Over WAN will work, but not sure how reliable will be. Regards.
BDR is asynchronous multi-master, without global transaction management etc.
XL is a distributed database with global transaction management, strong consistency, etc.
Say you have geographically distributed application (managing customers in US, EU, ...). You can deploy a node in each area and direct local users to this node with low latency etc. It also means "no conflicts" (which is a major concern in multi-master), and the changes will asynchronously replicate to the other nodes.
XL would perform poorly in this scenario (at least I believe so), and it's meant more for local deployments, when hitting vertical scalability limits.