In this paper, we propose a novel approach to manage the throughput vs visibility latency tradeoff that emerges when enforcing causal consistency in geo-replicated systems. Our approach consists in allowing full concurrency when processing local updates and using a deferred local serialisation procedure before shipping updates to remote datacenters. This strategy allows to implement inexpensive mechanisms to ensure system consistency requirements while avoiding intrusive effects on update operations, a major performance limitation of previous systems. We have implemented our approach as a variant of Riak KV. Our evaluation shows that we outperform sequencer-based approaches by almost an order of magnitude in the maximum achievable throughput. Furthermore, unlike previous sequencer-free solutions, our approach reaches nearly optimal remote update visibility latencies without limiting throughput.
