What is likely causing the timeouts?
The database is deployed in a VPC that is in a different Region.
The database is deployed in a VPC that is in a different Availability Zone.
The database is deployed with misconfigured security groups.
The database is deployed with the wrong client connect timeout configuration.
Explanations:
The VPC peering connection is valid, so the Region is not the issue. RDS instances can span different VPCs within the same region.
Availability Zones (AZs) don’t impact VPC peering connectivity, and instances across AZs within the same region can communicate without issues.
Misconfigured security groups are a common cause for connectivity issues. If the RDS instance security group does not allow inbound traffic from the other VPC’s CIDR block, the connection will timeout.
Client connect timeout configuration is unlikely to be the root cause of the timeout. The issue is more likely related to network connectivity or security group settings.