This section provides a comprehensive comparison between CNAME records and Alias records in AWS, highlighting their unique features, use cases, and limitations.

CNAME vs. Alias Records

• CNAME Records
  • Purpose: Allow a domain to point to any other hostname.
  • Use Case: Suitable for non-root domain names (e.g., something.mydomain.com).
  • Limitation: Cannot be used for the apex domain (e.g., mydomain.com).
• Alias Records
  • Purpose: Enable a domain to point directly to an AWS resource (e.g., Load Balancer, CloudFront).
  • Use Case: Works for both root domains (apex) and non-root domains.
  • Advantages:
    • Free of charge.
    • Integrated health check capability.
    • Automatically updates to reflect IP address changes of the target AWS resource.
  • Limitation: Cannot target EC2 DNS names directly.

Detailed Insights on Alias Records

• Specificity: Alias records are exclusive to AWS Route 53 and extend DNS functionality.
• Automatic TTL Management: TTL (Time to Live) settings are managed by Route 53, not the user.
• Targets:
  • Elastic Load Balancers (ELB)
  • CloudFront Distributions
  • API Gateway
  • Elastic Beanstalk environments
  • S3 Websites (not just buckets)
  • VPC Interface Endpoints
  • Global Accelerator
  • Other Route 53 records within the same hosted zone

Practical Example

The tutorial provided a hands-on example demonstrating how to set up both CNAME and Alias records in AWS Route 53:

• CNAME Example: Mapping myapp.stephanetheteacher.com to an ALB DNS name. This setup is typical but has limitations for apex domain mapping.
• Alias Record Example: Showcases how to map both a non-root domain (myalias.stephanetheteacher.com) and the apex domain (stephanetheteacher.com) to AWS resources like an ALB, highlighting Alias records' flexibility and cost-effectiveness.

Key Takeaways

• Domain Apex Handling: Alias records are uniquely capable of pointing the apex domain directly to AWS resources, overcoming the limitations faced by CNAME records.
• Cost and Health Checks: Alias records offer cost benefits (no charges for queries) and built-in health checks, making them advantageous for AWS-specific architectures.
• Exam Relevance: Understanding the distinctions between CNAME and Alias records, especially regarding apex domain handling, is crucial for AWS certification exams.

This comparison not only outlines the technical differences and applications of CNAME and Alias records in AWS but also provides practical insights into their setup and benefits, crucial for AWS architects and developers.

You can use a CNAME record to route api.example.com to your load balancer in Amazon Route 53. A CNAME record allows you to map one domain name (in this case, api.example.com) to another domain name, which would be the DNS name of your load balancer. This is a common practice for routing subdomains to AWS resources.

Here’s how you can set it up: