I don't know Scylla, but Aerospike is intentionally designed for low-latency networking [1] (i.e., typically colocated within a single rack), which can be a challenge in the cloud.
There is nothing Cloud-specific in Scylla, though.
Scylla will also target low latencies, and we have been very successful at that. But we also commit to supporting the Cassandra data model, so we won't really chase extra latencies if it means breaking that.