AWS Certified Solutions Architect Professional SAP-C02 Practice Question

TargetResponseTime is a built-in Application Load Balancer metric that records the time (in seconds) from when the request leaves the load balancer until the target starts to send the response headers. Because CloudWatch supports percentile statistics, an alarm on the p95 value of this metric with a 0.2-second threshold expresses the requirement that 95 % of requests finish within 200 ms. No application changes or additional infrastructure are required, so this solution meets the "least development effort" criterion.

Publishing a custom BookingLatency metric would also work, but it demands code changes, metric maintenance, and permissions. AWS X-Ray only provides average latency by default and does not expose the 95th percentile; enabling 100 % sampling can introduce overhead. An Auto Scaling policy that reacts to request count may reduce latency indirectly, but it does not measure or alarm on latency and therefore cannot prove the SLA is met.