Nameserver response timeWhat it checks and how to fix it

What it checks

Sends three non-recursive A-record queries to each of the domain's authoritative nameservers and times them. Passes when every nameserver averages 200 ms or less, warns when one averages over 200 ms (and over 500 ms is reported as slow), and fails when a nameserver answers none of the queries or no nameservers are found.

Why it matters

Every first visit starts with a DNS lookup, and a resolver that misses its cache has to ask your nameservers directly, so their response time adds straight to time to first byte. A nameserver that does not answer makes resolvers wait for a timeout before trying the next one, and a dead server left in your NS set is a single point of failure nobody notices until the others go down.

How to fix it

Host the zone on an anycast DNS provider (Cloudflare, AWS Route 53, Google Cloud DNS, NS1 and similar), which answer from a location near each resolver, and remove nameservers that no longer answer from both the zone and the delegation at your registrar.

Measure each nameserver yourself:

dig +short NS example.com
dig +norecurse A example.com @ns1.dns-provider.net | grep "Query time"

The NS records in your zone and the nameservers set at the registrar must list the same servers.