Unable to release Elastic IP stuck with "ServiceManaged: rds" – No active RDS resources found

The Elastic IP is likely still associated with RDS service-managed resources that may not be immediately visible in the RDS console. The "ServiceManaged: rds" tag indicates that RDS has control over this resource through its service-linked role.

Here are some additional steps to investigate and resolve this issue:

Check for Hidden RDS Resources:

1. Verify there are no DB instances in a "deleting" or transitional state by using the AWS CLI: aws rds describe-db-instances --region us-east-2
2. Check for DB clusters (Aurora): aws rds describe-db-clusters --region us-east-2
3. Look for custom DB cluster endpoints that might still exist: aws rds describe-db-cluster-endpoints --region us-east-2

Check Network Interfaces: Since RDS manages network interfaces that can hold EIPs, check for any lingering network interfaces:

• In the EC2 console, go to Network Interfaces and filter by the us-east-2 region
• Look for interfaces with a description containing "RDS" or with a "Requester ID" showing "amazon-rds"
• Check if any of these interfaces have your EIP associated with them

Verify VPC Endpoints: RDS can create VPC endpoints that might hold onto network resources. Run: aws ec2 describe-vpc-endpoints --region us-east-2 --filters "Name=service-name,Values=*rds*"

Service-Linked Role Permissions: The RDS service-linked role has permissions to manage EC2 resources including allocating, associating, and releasing addresses. However, there may be a delay or stuck state in the cleanup process.

Given that your support case has been unassigned for 12 days, I recommend:

1. Escalating your existing support case or opening a new one specifically mentioning the "ServiceManaged: rds" tag and the stuck EIP
2. Request that AWS Support check for any orphaned RDS-managed resources in your account
3. Ask them to verify the service-linked role's cleanup processes for this specific EIP

Unfortunately, you cannot directly force RDS to release service-managed resources without AWS Support intervention, as these are controlled by the service itself through its service-linked role policies.
Sources
AmazonRDSServiceRolePolicy - AWS Managed Policy