I am working on an application that will be used to verify new domains are configured correctly as they're set up for hosting. Part of this checks the validity of SPF, DomainKey, DKIM records, etc.
I currently use a default TTL of one hour for most of these records. Occasionally a mistake is found in one of the records so it needs to be updated. Currently, if I've just tested the domain I have to wait for the system's resolver's cached record to expire before I can verify it is correct with my application. (Yes, I can check manually but I wrote the application so I don't have to).
I would like to set up a DNS server on the system to act as a normal caching resolver except that it will expire records in a maximum of a set time such as five minutes or just not cache at all. Not all of the domains have DNS hosted on my normal name servers so this system would have to query the authoritative name servers for a domain rather that use upstream resolvers (which would just use their cached records).
This machine is not currently running DNS of any kind so I can install BIND or djbdns (or something else if there's a good suggestion.