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DNS Architecture in Cloud Computing

Learn about DNS Architecture in this comprehensive Cloud Computing tutorial. Advanced routing.

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1Alias vs CNAME

You cannot create a CNAME for a root domain (zone apex) like 'example.com' due to DNS protocol limitations. AWS created Alias records to solve this exact problem, allowing you to map the apex to an ALB or CloudFront distribution.

2Step-by-Step Breakdown

What is Route 53?. A highly available and scalable cloud Domain Name System (DNS) web service. (Port 53 is the standard DNS port).

Hosted Zones. A container for records that define how to route traffic for a domain.

A Records vs CNAME. An 'A' record maps a hostname to an IPv4 address. A 'CNAME' maps a hostname to another hostname.

Alias Records. AWS-specific records that map your root domain (example.com) directly to AWS resources like ALBs or CloudFront.

Knowledge Check. What AWS-specific DNS record allows you to map a root domain to an Application Load Balancer?

→CNAME Record
→Alias Record

Simple Routing. Standard DNS function. Returns one or multiple IP addresses for a single domain name.

Weighted Routing. Splits traffic based on assigned weights. Great for A/B testing or gradual blue/green deployments.

Latency & Geolocation. Latency routing sends users to the AWS region with the lowest latency. Geolocation routes based on user location (e.g., Europe traffic stays in EU).

Failover Routing. Monitors health checks. If the primary endpoint fails, traffic is routed to the secondary (disaster recovery) endpoint.

Summary. Route 53 is your global traffic cop, ensuring high availability.

Pascual Vila

Frontend Instructor // Code Syllabus

Common Pitfalls & Errors

The Error //

Setting a low TTL only after realizing you need to change a record quickly

aws route53 change-resource-record-sets --hosted-zone-id Z123456 \
  --change-batch '{"Changes":[{"Action":"UPSERT","ResourceRecordSet":{"Name":"app.example.com","Type":"A","TTL":60,"ResourceRecords":[{"Value":"1.2.3.4"}]}}]}'

The Solution //

A high TTL set on a record means any future emergency change (like a failover or an IP migration) takes hours to propagate, since resolvers cache the old value. Set an appropriately low TTL in advance on any record that might need a fast change later — you can't retroactively shorten a cache that's already been read.

The Error //

Using a Simple routing policy when a Weighted or Failover policy is actually needed

// Failover policy requires an associated health check
aws route53 create-health-check --caller-reference 2026-01 \
  --health-check-config Type=HTTPS,ResourcePath=/health,FullyQualifiedDomainName=app.example.com

The Solution //

Simple routing returns one static answer with no health checking — if that endpoint fails, DNS keeps sending traffic to it. For any multi-endpoint or high-availability setup, use Weighted (gradual rollout), Latency, or Failover routing policies with health checks attached.