Aurora cluster has fewer than two instances — no Multi-AZ failover target

What it checks

Aurora cluster declares fewer than two cluster instances.

Where it applies

Terraform: aws_rds_cluster

CloudFormation: AWS::RDS::DBCluster

How to fix it

1. Add a second aws_rds_cluster_instance (or set count = 2 on the existing one). Aurora promotes a replica automatically on writer failure.
2. For non-Aurora engines needing managed HA, consider a Multi-AZ DB cluster (db_cluster_instance_class) — one writer plus two readable standbys.

Frameworks

• AWS FSBP RDS.15
• SOC 2 A1.2
• SOC 2 CC7.4
• NIST 800-53 rev5 CP-10
• NIST 800-53 rev5 SC-5(2)

These mappings are advisory, not an attestation of compliance.

Vendor documentation

All rules