[room271]

No. The choice of datastore is still incredibly complicated in the distributed world; it's all about tradeoffs really.

For example, Elasticsearch has poor availability characteristics - both because it is master-slave and because it focuses on ensuring consistency - relative to, for example, something like Riak.

[kainosnoema]

I don't believe it's "master-slave" in the way you're thinking. Elasticsearch shards its indexes among all available nodes, storing replicas of each shard on separate nodes when possible. This ensures that the entire cluster is available as long as at least one replica of a shard is still online. In fact, if configured properly, it has better availability than consistency since by default it only flushes its oplog to the Lucene index segments every second (though writes aren't considered committed until they reach a quorum of nodes, so consistency is fairly good in practice as well).