which AZ does RDS instance deploy in if DB Subnet group contains both public/private subnets

Question

If i have a MultiAZ MySQL RDS on a DB subnet group which contains 2 subnets (1 public subnet & 1 private subnet), what happens when a reboot with failover is performed?

Let's assume my RDS is public facing and it receives requests from the world and not from just my VPC or Subnet or AWS.

Typically i understand, a primary DB instance will be in one AZ/subnet and a secondary standby DB instance will be in another AZ/subnet. So if a reboot with failover is performed, the secondary will become the primary and all IO requests will go to the new primary. So, if one of the subnet in my DB subnet group was private, how will it receive requests from the world if the primary DB instance ends up being in the private subnet?

Answer 1

So, if one of the subnet in my DB subnet group was private, how will it receive requests from the world if the primary DB instance ends up being in the private subnet?

It won't. Add a public subnet in the second zone.