I made a MySQL RDS DB Instance, and I made sure the Instance is inside a security group which should allow me to connect to it externally. The security group allows all types of traffic from all IP addresses. The RDS is in the same security group as an EC2 I made.
I'm able to connect to the DB Instance by connecting to the EC2 via SSH, then using the mysql CLI client I installed on that EC2 to connect to the RDS. However, I'm not able to connect directly to the RDS from a MySQL client on my personal computer. I use the same host and username and all for the RDS, but circumventing the EC2 doesn't work.
From googling around, it seem like the error I'm getting is usually caused by the RDS's security group not allowing traffic from my computer - but this can't be the case, because I triple checked that the security group is open to all public traffic. Heck, the RDS is in the same security group as the EC2, and I'm able to connect to the EC2.
So what's going on?