AWS, Azure & GCP · Cloud across providers
How does DNS work in the cloud?
Short answer
DNS maps names to records such as A, AAAA, CNAME and MX, resolved through a hierarchy of authoritative servers. Cloud DNS services add health checks, routing policies and private zones.
A resolver asks the DNS hierarchy for an answer: root, then the top-level domain, then the authoritative name server for the zone. The answer is cached for the record's TTL, which is why changes are not instant everywhere.
Records you will use
- A and AAAA map a name to IPv4 and IPv6 addresses
- CNAME maps a name to another name, and cannot coexist with other records at the same name
- MX routes mail, TXT carries verification and policy data
- Alias records point to provider resources without hard-coding an IP
dig api.example.com A +short
dig api.example.com CNAME +short
dig +trace api.example.comCloud DNS adds routing policies such as failover, weighted, latency and geolocation. Health-checked failover can move traffic to a standby, but low TTLs increase query volume and are not a substitute for a working failover plan.
Follow-ups you should expect
Interviewers use these to check whether the first answer was understanding or memorisation.
- 1Why does a DNS change take time to propagate?
- 2What is the difference between a CNAME and an alias record?
- 3How does health-checked failover routing work?
- 4When would you use a private hosted zone?
Say it in the interview
DNS resolves names through a hierarchy of authoritative servers, and resolvers cache answers for the TTL. Cloud DNS adds routing policies like failover, weighted and latency, plus private zones. I use alias records for provider resources, keep TTLs appropriate for the change rate, and remember that DNS failover is only as good as the health check and the standby behind it.
Use this as a model, not a script. Saying it in your own words is what makes it survive follow-up pressure.
Related questions
Reading is step one
Now say it out loud.
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