I know this is a pretty low-level question, but seems like couchbase is all about the extreme-performance plays 
Have you ever skunked out a CB instance on a Infiniband network using an RDMA driver for Erlang? https://github.com/iamjamestl/rdma_dist
Azure has made a pretty heavy investment in RDMA virtual machines. I don’t know a ton about the inner “guts” of couchbase, but I would assume that latency is king in just about any distributed system.