pointing Ec2 public ip address to my domain using A record

When I look at your domain and try to find the NS records, I find nothing:

% dig -t NS techdomain.link

; <<>> DiG 9.10.6 <<>> -t NS techdomain.link
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 13364
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;techdomain.link.		IN	NS

Asking the root servers for .link about techdomain.link, they provide a name-server set of:

% dig @ns4.uniregistry.info. -t NS techdomain.link

; <<>> DiG 9.10.6 <<>> @ns4.uniregistry.info. -t NS techdomain.link
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 61768
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 4, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;techdomain.link.		IN	NS

;; AUTHORITY SECTION:
techdomain.link.	900	IN	NS	ns-1971.awsdns-54.co.uk.
techdomain.link.	900	IN	NS	ns-739.awsdns-28.net.
techdomain.link.	900	IN	NS	ns-472.awsdns-59.com.
techdomain.link.	900	IN	NS	ns-1313.awsdns-36.org.

Which match the ones that are in whois when I check the registration. Now if I ask one of those name-servers for the NS records for techdomain.link, they give an recursive failure:

% dig @ns-1971.awsdns-54.co.uk. -t NS techdomain.link

; <<>> DiG 9.10.6 <<>> @ns-1971.awsdns-54.co.uk. -t NS techdomain.link
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 27271
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;techdomain.link.		IN	NS

;; Query time: 23 msec
;; SERVER: 205.251.199.179#53(205.251.199.179)
;; WHEN: Thu Aug 24 13:48:08 CEST 2023
;; MSG SIZE  rcvd: 33

This means that your domain registration at AWS does not contain the correct NS records (delegation set) of the Route53 hosted zone for techdomain.link.

Navigate to your Route53 console, and find the public hosted zone for techdomain.link where you have created your A-record. Copy the 4 NS record names from there to a text file. Then navigate the the Route53 domains page, where you bought techdomain.link in your AWS Console. Update the name-server records for the registered domain techdomain.link to match those that you copied to a text file earlier.

Wait for the DNS to replicate - this could take 24 - 48 hours and then it should work.