🔁 Metric #2: Application Error Rate via X-Ray Traces. Use X-Ray segment annotations for a custom error rate metric (you would emit this yourself via PutMetricData):

traces.tf

resource "awscc_applicationsignals_service_level_objective" "app_error_rate" {
  name        = "app-error-rate-slo"
  description = "Application error rate derived from X-Ray segments"

  sli = {
    comparison_operator = "LessThan"
    metric_threshold    = 1.0 # <1% errors

    sli_metric = {
      metric_data_queries = [{
        id = "errorrate"
        metric_stat = {
          metric = {
            namespace   = "MyApp/XRay"
            metric_name = "ErrorRate"
            dimensions = [
              {
                name  = "ServiceName"
                value = "MyFargateService"
              }
            ]
          }
          period = 300
          stat   = "Average"
        }
      }]
    }
  }

  goal = {
    attainment_goal = 99.0
    interval = {
      rolling_interval = {
        duration      = 7
        duration_unit = "DAY"
      }
    }
  }

  burn_rate_configurations = [
    { look_back_window_minutes = 60 },
    { look_back_window_minutes = 1440 }
  ]
}