Well, it depends on how far your datacenters are - in the end you're still limited by the laws of physics (speed of light). So 'fast' may actually be several ms

Well, it depends on how far your datacenters are - in the end you're still limited by the laws of physics (speed of light). So 'fast' may actually be several ms, which might be a lot, or not a lot, depending on the problem you're trying to solve.