A financial services company runs an active-active application across us-east-1 and eu-west-1. Each region has an Application Load Balancer fronting an ECS service. They use Route 53 latency-based routing with health checks pointing at each ALB. During a partial regional degradation, the ECS tasks in eu-west-1 remained running and passed ALB target group health checks, but a critical downstream dependency (a regional payment API) was returning HTTP 500 errors. Route 53 continued sending European users to the failing region. The DevOps team must ensure Route 53 stops routing to a region when the application is functionally unhealthy, even if the ALB and tasks appear healthy. What is the MOST effective solution?