AWS SOA-C02 Drill: Route 53 Routing - Cost-Effective NLB Alias Record

The Jeff’s Note (Contextual Hook)

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Jeff’s Note

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Unlike generic exam dumps, ADH analyzes this scenario through the lens of a Real-World Site Reliability Engineer (SRE).

For SOA-C02 candidates, the confusion often lies in selecting the correct Route 53 record type to efficiently and cost-effectively route traffic to a Network Load Balancer. In production, this is about knowing exactly which DNS record type is a Route 53 alias and its cost benefits over CNAME or other records when fronting an NLB. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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CloudShift Solutions operates a public-facing web application hosted behind a Network Load Balancer (NLB). The NLB is internet-facing but does not have any Elastic IP addresses assigned to it. Users must access the application using the company’s branded domain name (e.g., www.cloudshift.com). The Site Reliability team needs to configure DNS entries in Amazon Route 53 to direct traffic to the NLB while minimizing ongoing DNS query costs.

The Requirement:

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Determine the MOST cost-effective and operationally sound Route 53 configuration to map the company domain name to the NLB.

The Options

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• A) Create a Route 53 AAAA record pointing to the NLB.
• B) Create a Route 53 alias record pointing to the NLB.
• C) Create a Route 53 CAA record pointing to the NLB.
• D) Create a Route 53 CNAME record pointing to the NLB.

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Correct Answer

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B) Create a Route 53 alias record pointing to the NLB.

Quick Insight: The Site Reliability Imperative

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• When routing to AWS resources like Network Load Balancers, Route 53 alias records provide a native integration that routes traffic efficiently and without extra DNS query charges.
• CNAME records introduce additional DNS lookups and incur costs, while CAA records are unrelated to routing.
• AAAA records specify IPv6 addresses directly, but NLBs don’t offer fixed IP addresses to reference manually.

Content Locked: The Expert Analysis

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You’ve identified the answer. But do you know the implementation details that separate a Junior from a Senior?

The Expert’s Analysis

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Correct Answer

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Option B: Create a Route 53 alias record pointing to the NLB.

The Winning Logic

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• Route 53 alias records are a Route 53-specific feature that lets you map your domain name directly to AWS resources such as NLBs, ALBs, S3 buckets, and CloudFront distributions.
• Alias records are served from authoritative Route 53 DNS servers and do not incur additional DNS query charges unlike CNAME or standard records.
• NLBs don’t have fixed IP addresses that you can hardcode into an A or AAAA record. Therefore, aliasing the NLB target DNS name allows Route 53 to resolve the changing IP addresses transparently.
• Alias records support zone apex (naked domain) routing, unlike CNAME records which cannot be used at the root domain.
• Using an alias record improves DNS resolution latency and reduces cost for high query volumes.

The Trap (Distractor Analysis):

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• Why not A (AAAA record)?
  NLB IP addresses are dynamic and not static fixed IPs you can point an AAAA record to. Also, this only covers IPv6, missing IPv4 users.

• Why not C (CAA record)?
  CAA records are Certificate Authority Authorization records used for restricting which CAs can issue certificates for a domain—not for routing traffic.

• Why not D (CNAME record)?
  CNAME records introduce an extra DNS lookup, cannot be used at the zone apex (root domain), and incur DNS query costs. They are less cost-efficient and operationally less ideal than alias records for AWS resources.

The Technical Blueprint

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# Example CLI command to **create an alias record** in Route 53 pointing to a Network Load Balancer
aws route53 change-resource-record-sets --hosted-zone-id Z3AADJGX6KTTL2 --change-batch '{
  "Changes": [{
    "Action": "UPSERT",
    "ResourceRecordSet": {
      "Name": "www.cloudshift.com",
      "Type": "A",
      "AliasTarget": {
        "HostedZoneId": "Z26RNL4JYFTOTI",  # NLB Hosted Zone ID (varies per region)
        "DNSName": "my-nlb-1234567890.us-east-1.elb.amazonaws.com",
        "EvaluateTargetHealth": false
      }
    }
  }]
}'

The Comparative Analysis

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Real-World Application (Practitioner Insight)

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Exam Rule

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“For the exam, always pick Route 53 Alias records when routing domain names to AWS resources such as NLBs.”

Real World

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“In production, alias records significantly simplify DNS management by automating updates to IP addresses behind the scenes and eliminating query charges.”

(CTA) Stop Guessing, Start Mastering

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Disclaimer

This is a study note based on simulated scenarios for the SOA-C02 exam.