Diagnostics / DNS Lookup, using Resolver, always shows Query time 0 msec
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Zero TTL allows to answer the query while relooking up the record after it answers... It hands the client the 0 ttl so new entry will be gotten next time client asks.
So in typical case where the IP has not changed and the TTL has just expired, client gets what it wants and can talk to the IP it needs to talk to.. If its no longer working - that would fail and the client would ask again anyway since the TTL was handed to it as ZERO.
By this time the resolver has gotten new IP with fresh ttl, etc.
Where it can help is those odd ball look ups where the NS for the domain are not the best.. So this allows the client to get a instant answer... Vs having to wait for possible extra ms for it to be resolved - just because it hasn't been a very looked up record and was not prefetched, etc.
Then next time the client asks it will get whatever the normal TTL on the record is.. It should help with some of the pesky domains that users might have complained they had to hit refresh in their browser, etc some of these domains NS are pretty shitty ;) So sometimes it can be delayed resolving directly.. It can help with those for sure... You would have to look at your stats to see if you have some NS with high long response times or time outs, etc.
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@johnpoz Got it! In that case, I'll enable 'em both. Thanks!
