Can't connect to EC2 Postgresql instance unless I change the default port 5432
Doing an nmap over the EC2 instance:

nmap -Pnv -p 5432 &lt;public-ip&gt;


revealed that my ISP is intentionally blocking the port 5432(third-world country FTW...):

Host is up.
PORT     STATE    SERVICE
5432/tcp filtered postgresql


It was never a problem with EC2 nor Postgresql in first place.