It's linked in the article, here is more links:
It's a very complex thing to implement, and unless they have made leaps beyond what Galera has done, for some workloads it will be fast, but for others it will perform far worse than a standard MySQL instance.
Of course, I guess it could also be a cluster built upon NDB, but the lack of memory constraints on the size of the data makes that less likely.
So, the ACI components of ACID are all done at the database tier using (largely) traditional techniques. Durability is where we're using distributed systems techniques around quorums, membership management, leases, etc, with the important caveat that we have a head node generating LSNs, providing a monotonic logical clock, and avoiding those headaches.
Our physical read replicas receive redo log records, update cached entries and have readonly access to the underlying storage tier. The underlying storage is log-structured with nondestructive writes, so we can access data blocks in the past of what is current at the write master node - that's required if the replica needs to read a slightly older version of a data block for consistency reasons.
Make sense?