JEPSEN

MongoDB 3.6.4

2018-10-22

We worked with MongoDB to explore sharded single-document consistency and MongoDB’s new support for causally consistent sessions. We found that sharded clusters appeared to preserve single-document linearizability and did not lose inserted documents during shard rebalancing and network partitions. However, causal sessions required majority reads and writes; at the default consistency levels, causal sessions did not preserve claimed ordering invariants. MongoDB has updated their documentation to reflect this.