Make sure to verify that the routes are correctly set up in the subnet where your RDS instance is located. To do this: • Go to the VPC settings in your AWS Console. • Navigate to Subnets and select the subnet where your RDS instance is located. • Click on Route Tables.

There should be a route similar to this: • Destination: 172.26.0.0/16 • Target: pcx-******** (your VPC peering connection).

For some reason, when a peering connection is created, it doesn’t automatically add routes for subnets associated with an Internet Gateway (if that’s your case). You’ll need to manually add the route to enable communication.