bind performance guideline

[Richard Z]

I am trying to find some design guidelines for bind. I only use ipv4.
Since I use application failover using dns, the TTL is set very low,
e.g. 60s. So the query volume is pretty high. I understand that bind
loads all domain records into memory. Anyone knows how much memory is
required for running N domains with less then 10 records for each
domain? How long does it take to load the text files into memory when
a new domain is added or records changed on a normal server CPU?

Thanks,