[manigandham]

Ultimately the same foundations of a globally distributed key/value store. Scylla is the Cassandra is a mashup of BigTable/Dynamo wide-column advanced key/value design allowing for very high scalability and availability, but the data model and querying abilities are not as flexible. Scylla does have variable per-query consistency settings but is primarily eventually consistent. Does support BATCH statements which are atomic updates, but no Lightweight-Transactions yet to read-before-write, but does have counters now. It's not quite feature parity with Cassandra but quickly getting there.

CockroachDB also uses a key/value store but puts a postgres-compatible SQL layer on top, derived from the Google Spanner approach, so you can get (almost) all the querying abilities and data modeling of a relational database. They're slated to have JSON datatypes soon that will make it very compelling as a general purpose, highly reliable datastore for all of your core data in multiple regions.