Connection to MariaDB server gets a timeout, out of nowhere.

Luckily I'm just working on a new side project. I didn't change the security group previously, as everything was connecting fine, but I added a rule to open up the DB completely and I can connect now. Would love an explanation how that could have changed?

And now it still randomly times out. Frustrating. This is just a vanilla public RDS instance.

Not positive, but I might have been DOSing the RDS instance because of a missing effect dependency. Oops. :P