I tested this pretty extensively. When I switched IPs, 99.9% of the HTTP traffic hit the new servers within the TTL time (5min). The only residual traffic hitti

I tested this pretty extensively. When I switched IPs, 99.9% of the HTTP traffic hit the new servers within the TTL time (5min). The only residual traffic hitting the old IPs I saw was from poorly configured bots & webspiders who probably don't re-resolve hostnames frequently enough. I remember also reading a post from Amazon EC2 Route 53 engineers who investigated DNS propagation times across large-scale tests in the world, and my observations aligned with theirs. They concluded the "DNS doesn't propagate according to TTL" story is mostly a myth (modulo rare issues here and there).