DNS from Request to Response

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Why this matters

DNS is the most-cached system in your stack and the one engineers least understand — TTLs you set today govern how fast a failover takes effect tomorrow. Negative caching means a typo'd record propagates a no-answer for 5 minutes by default, and recursive resolvers in front of your users won't refresh just because you fixed it.

Demo

Trace a DNS query end-to-end through the recursive resolver chain.

Try it yourself

Run dig +trace example.com and label each hop: root, TLD, authoritative.
Query a non-existent subdomain twice — note the SOA minimum TTL controlling negative cache duration.
Drop a record's TTL from 3600 to 60 in a non-prod zone and time how long old answers persist on a public resolver.

References

# Route 53 hosted zones
aws route53 list-hosted-zones --query 'HostedZones[*].[Name,Id]' --output table

# Inspect a record's TTL
aws route53 list-resource-record-sets --hosted-zone-id <zone-id> \
  --query 'ResourceRecordSets[?Type==`A`].[Name,TTL]' --output table

# Trace resolution from root → TLD → authoritative
dig +trace example.com

# Check what your local resolver sees (and its TTL countdown)
dig example.com +noall +answer