Difference Between Alias and CNAME Records in Route 53 :
Both Alias and CNAME (Canonical Name) records are used in DNS to map one domain name to another. However, there are key differences in functionality, usage, and support within Amazon Route 53.
1. Alias Record :
- Purpose: Alias records are a Route 53-specific feature used to map a domain name to an AWS resource, such as an S3 bucket, a CloudFront distribution, an Elastic Load Balancer (ELB), or another Route 53 record in the same hosted zone.
- DNS Resolution: Alias records resolve directly to an IP address. Route 53 automatically updates the record if the underlying AWS resource's IP address changes.
- Top-Level Domains: Alias records can be used for the root domain (apex domain), such as
example.com, without requiring a third-party workaround.
- Cost: Queries to Alias records for AWS resources are free.
- Use Case:
- Mapping the root domain (
example.com) to an AWS resource like an ELB or CloudFront.
- Mapping subdomains (e.g.,
app.example.com) to AWS resources.
2. CNAME Record :
- Purpose: CNAME records map a domain name to another domain name (canonical name), which then resolves to an IP address.
- DNS Resolution: CNAME records resolve to another domain name and not directly to an IP address.
- Top-Level Domains: CNAME records cannot be used for root domains (apex domains) like
example.com. They can only be used for subdomains, such as www.example.com or api.example.com.
- Cost: Standard DNS queries are charged.
- Use Case:
- Redirecting a subdomain (
www.example.com) to another domain name or third-party service.
- Mapping subdomains to non-AWS services like
www.example.com → example.external-service.com.
