Route53: Where are SOA records, NS records stored?

Question

Route 53 is supposed to be an Authoritative Name Server as per the AWS docs. If example.com is the domain that I have bought, and I have www.example.com pointing to an IP 1.2.3.4, then, the Top Level Domain Name Server(the NS for ".com") stores a mapping between the Authoritative Name Server (ANS) for the domain example.com and the domain example.com as shown below:  
  
example.com. 172800 IN NS ns1.awsdns.com  
  
So, this is the NS record and this NS record is sitting in the TLD Name Server for ".com". Is my understanding right? If yes, then, why do I also get to see the same record in the Route 53 Console? Route 53 is supposed to be an Authoritative Name Server. Why does an Authoritative Name Server need to keep pointers about the example.com domain being served by itself? Isn't the fact that the ANS for the domain example.com is ns1.awsdns.com, needs to be known to the .com TLD NS and not Route53 itself?  
  
Also, where would the SOA record reside? Would it reside in the ANS itself? Below is an SOA record:  
  
ns1.awsdns.com admin.awsdns.com 2013022001 86400 7200 604800 300  
  
This has the:  
  
The primary name server for the domain: ns1.awsdns.com  
  
The responsible party for the domain: admin.awsdns.com  
  
timestamp that changes whenever you update your domain: 2013022001  
  
The number of seconds before the zone should be refreshed: 86400  
  
The number of seconds before a failed refresh should be retried: 7200  
  
The upper limit in seconds before a zone is considered no longer authoritative: 604800  
  
The negative result TTL: 300  
  
If this SOA record is sitting in the ANS itself, that is in the ns1.awsdns.com machine itself, then what is the point of this SOA record telling the ANS ns1.awsdns.com that ns1.awsdns.com is the primary name server?  
  
Can someone clear the confusion here? I am utterly confused.

Answer

As the DNS protocol is designed, **both** the parent (in this case, the TLD) and the child (in this case, your zone using Route 53) have a copy of the NS records. As you've realized, the child-side NS records are technically superfluous, but the rule is that they must exist, so they do.  
  
(They're supposed to be identical, but it's not really possible to technically enforce that.)  
  
I haven't found anyone who knows _why_ it was designed that way. There was probably a good reason for it, which may or may not apply to how the DNS is used 35 years later.  
  
The SOA record exists in the child zone. The primary nameserver is used for some things -- such as discovering which nameserver to send RFC 2136 dynamic updates to -- but you're probably not using it for anything when using Route 53. (For example, Route 53 is configured through the AWS API, not through RFC 2136 dynamic updates.)

Answer

Thanks a lot! Gives me the clarity

Route53: Where are SOA records, NS records stored?

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