What is the difference between a CNAME and an Alias record in Route 53?
AWS · Intermediate level
Answer
A CNAME maps a DNS name to another name and usually cannot be used at the zone apex. A Route 53 Alias points to AWS resources, can be used at the apex, and is preferred for ALB, CloudFront, API Gateway, and similar targets.
Technical explanation
Alias records are AWS-specific and can be used at the zone apex where CNAME normally cannot.
DNS and CDN design must account for caching behavior, TTLs, origin protection, health signals, TLS, and global user latency.
Route 53 routing policies and CloudFront cache policies should be chosen based on the real traffic-management goal, not because they are available.
Always test failover, cache invalidation, header/cookie/query-string behavior, and origin access controls before production cutover.
Hands-on example
1. Create a test hosted zone or subdomain and route traffic to a controlled ALB, API, S3/CloudFront origin, or secondary Region.
2. Configure the relevant policy - weighted, failover, alias, cache behavior, OAC, or health check - and keep TTLs low during testing.
3. Use dig/curl and CloudFront/Route 53 logs or metrics to verify routing, caching, TLS, and failover behavior.
4. Increase TTLs and tighten origin access after validation.
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