not sure if it applies but depending on instance type I usually see pings in the .55ms range in a single AZ in AWS, cross-AZ pings higher (implying it is hard to be sub ms for many types of durable applications, especially if disk/S3 is involved)
However, if you're considering a multi-region setup, the latency will depend on the distance between the regions.That's why usually you define a preferred region (that stores primary copy of the records) or deploy in a geo-partitioned mode (when data is automatically pinned to configured regions).