Question 650
Autoscaling must respond to real user experience rather than noisy counters. The team confirms that the autoscaling group cannot launch more instances because all subnet IPs are exhausted. What should the solution architect recommend?
Explanation
Correct Answer
The scenario identifies this requirement: The autoscaling group cannot launch more instances because all subnet IPs are exhausted. Select Expand subnet IP capacity or placement design before further scale-out as the specified technical mechanism. Scale-out requires free addresses in selected subnets. This response addresses the problem described rather than a different design goal.
Incorrect Answers
The option Use appropriate metric windows and cooldowns/warmup settings addresses a separate condition: a service CPU metric has periodic spikes that trigger needless rapid scaling. Scaling stabilization prevents thrashing. The actual requirement is the autoscaling group cannot launch more instances because all subnet IPs are exhausted. Recommended corrective action: Expand subnet IP capacity or placement design before further scale-out. Scale-out requires free addresses in selected subnets.
For the alternative failure a scheduled ETL job creates a predictable burst of API calls each night, the control Pre-scale capacity with scheduled actions around the ETL window is relevant: scheduled scale reduces predictable burst delays. Here the evidence instead is the autoscaling group cannot launch more instances because all subnet IPs are exhausted. The selected technical mechanism is Expand subnet IP capacity or placement design before further scale-out: scale-out requires free addresses in selected subnets.
Use backlog-per-consumer or oldest-message age scaling signals solves a different operational problem where queue lag grows despite average CPU below 20 percent. Queue lag measures processing shortage directly. It does not directly address the autoscaling group cannot launch more instances because all subnet IPs are exhausted. The case calls for Expand subnet IP capacity or placement design before further scale-out, since scale-out requires free addresses in selected subnets.