The DNS request first goes to the Primary DNS and will check the Secondary DNS if the Primary does not provide the address it was looking for.
Since we're talking about Google here for a client-side implementation of their DNS and even as a resolver for a server, we can be certain the Google has properly distributed their DNS and has all of these optimally optimized!
Things to consider in choosing a DNS considering performance.
- How many Servers are they running?
- Are they properly distributed and using Anycast?
- Are the Servers close to your location?
Google has Servers all around the world. Here's a list of Google DNS Servers. This makes the DNS server run faster compare to other DNS provides with smaller networks.
74.125.16.0/24 tpe
74.125.17.0/24 bru
74.125.18.0/24 grq
74.125.19.0/24 mrn
74.125.40.0/24 mrn
74.125.41.0/24 tpe
74.125.42.0/24 atl
74.125.43.0/24 tul
74.125.44.0/24 mrn
74.125.45.0/24 tul
74.125.46.0/24 lpp
74.125.47.0/24 bru
74.125.72.0/24 cbf
74.125.73.0/24 bru
74.125.74.0/24 lpp
74.125.75.0/24 chs
74.125.76.0/24 cbf
74.125.77.0/24 chs
74.125.78.0/24 chs
74.125.80.0/24 dls
74.125.113.0/24 cbf
74.125.114.0/24 mrn
74.125.176.0/24 mrn
74.125.177.0/24 atl
74.125.178.0/24 atl
74.125.180.0/24 chs
74.125.181.0/24 bru
74.125.182.0/24 cbf
74.125.183.0/24 cbf
74.125.184.0/24 chs
74.125.185.0/24 chs
74.125.186.0/24 dls
74.125.187.0/24 dls
74.125.190.0/24 sin
173.194.89.0/24 tul
173.194.90.0/24 cbf
173.194.91.0/24 scl
173.194.92.0/24 bru
173.194.93.0/24 tpe
173.194.95.0/24 tul
173.194.96.0/24 dub
173.194.98.0/24 lpp
173.194.99.0/24 tul
2001:4860:400b::/48 dls
2404:6800:4003::/48 sin
2404:6800:4008::/48 tpe
2607:f8b0:4001::/48 cbf
2607:f8b0:4002::/48 atl
2607:f8b0:4003::/48 tul
2607:f8b0:400c::/48 chs
2607:f8b0:400d::/48 mrn
2607:f8b0:400e::/48 dls
2800:3f0:4003::/48 scl
2a00:1450:400b::/48 dub
2a00:1450:400c::/48 bru
2a00:1450:4010::/48 lpp
2a00:1450:4013::/48 grq
Google Public DNS uses anycast routing to direct all packets to the closest DNS server. About anaycast here
Since Google's servers are globally distributed, there is a high chance of one being close to you.