In the Amazon Route 53 docs (Opening connections to an Amazon RDS database instance using your domain name) – I see there is a restriction to use CNAME record to associate to a domain name (You must use a CNAME record to associate a domain name with an Amazon RDS DB instance. Route 53 doesn’t support using other types of records for this purpose.)
I do not understand this restriction and why , unlike several other AWS services (ELB, S3, CF) – I cannot use alias record.
Any insights to this would be highly appreciated
I don’t think is any technical issue here. It is simply that AWS do not offer this option.
From my perspective it would not be very common to expose your DB instance to the internet without an intermediary. so there is limited demand for this capability, and the use of a CNAME would meet those cases.