C is correct because it converts the single–Availability Zone, single-EC2-instance ECS design into a managed, multi-AZ, self-healing architecture with minimal day-to-day operations. The current design has multiple single points of failure: one EC2 instance for ECS capacity and one Availability Zone for all components. Moving the ECS service to AWS Fargate removes the need to manage EC2 instances (capacity provisioning, patching, and scaling of the container instances) and allows the service to run tasks across multiple Availability Zones for higher availability. On the database side, modifying Aurora PostgreSQL to a Multi-AZ DB cluster (by adding a replica in another AZ) increases availability and supports faster recovery from an AZ failure with AWS-managed failover.
Why the other options are less suitable:
A: Making Aurora Multi-AZ improves database availability, but it does not address the compute layer’s biggest issue: ECS is on a single EC2 instance in one AZ with no auto scaling. RDS Proxy can help with connection management, but it does not fix the application’s single-AZ ECS single-instance availability risk.
B: Cross-Region read replicas and manual failover scripts increase operational burden. Also, it keeps ECS on EC2 (still requires instance management) and introduces a manual failover process, which is the opposite of “least operational overhead.”
D: Multi-Region active-active plus Aurora global database can deliver very high availability, but it adds significant complexity (multi-Region deployment, routing strategy, global database considerations, operational procedures). That is higher operational overhead than a straightforward multi-AZ design using managed services.
[References:, Amazon ECS Documentation: service placement across multiple Availability Zones; high availability patterns for ECS services, AWS Fargate Documentation: serverless container compute that removes the need to manage EC2 instances and supports multi-AZ task placement, Amazon Aurora PostgreSQL Documentation: Multi-AZ Aurora architecture, replicas across Availability Zones, and managed failover behavior, AWS Well-Architected Framework (Reliability Pillar): eliminating single points of failure with multi-AZ architectures and using managed services to reduce operational burden, AWS Certified Solutions Architect – Professional (SAP-C02) Exam Guide: designing highly available workloads, selecting managed services to reduce operational overhead, , , , ]
