> Thus far, causal consistency has generally been limited to research projects ... MongoDB is one of the first commercial databases we know of which provides an implementation.
Cosmos DB provides session consistency (looks like an another name for causal consistency) at least since 2014 [1].
Causal and session are definitely similar, but I'm not entirely sure if causal implies consistent prefix, and conversely, I think causal miiight have stronger implications than just the intersection of MR, MW, RYW, and WFR. Because we weren't entirely certain whether we could make that claim regarding Cosmos, we opted to be conservative.
I agree it's hard for me too to be precise about naming in academic sense. But this published paper "Writes: the dirty secret of causal consistency" says that both Cosmos DB and MongoDB have causal consistency so I don't know.. At least Cosmos DB and MongoDB provide the same guarantees for session/causal.
To clarify: no, Jepsen, as an organization, has not worked with CosmosDB.
I'm delighted they have rigorous tests, and I'm glad our tool has been helpful for them! We just can't say anything about those tests, because we haven't looked yet. Maybe someday!
Cosmos DB provides session consistency (looks like an another name for causal consistency) at least since 2014 [1].
Cosmos DB's session guarantees [2]: consistent prefix, monotonic reads, monotonic writes, read-your-writes, write-follows-reads.
Mongo DB's causal consistency guarantees [3]: monotonic reads, monotonic writes, read-your-writes, write-follows-reads.
Doubt that four years later still qualities as one of the first.
[1] https://www.infoq.com/news/2014/08/microsoft-azure-documentd...
[2] https://docs.microsoft.com/en-us/azure/cosmos-db/consistency...
[3] https://docs.mongodb.com/manual/core/read-isolation-consiste...