SAA-C03 practice question: EC2 Auto Scaling (2 of 3)

Design Resilient Architectures A free question from our original SAA-C03 practice exam. Try it, then open the answer to see why each option is right or wrong.

A university runs its online exam portal on Amazon EC2 instances in an Auto Scaling group with a target tracking policy on CPU use. Exams take place on dates published a month in advance, with no regular weekly pattern, and thousands of students log in at exactly 09:00 on those days. New instances take about 8 minutes to boot and load the application, so students see errors at the start of each exam. Enough capacity must be in service before 09:00 on exam days. What should a solutions architect do?

Choose one answer.

A. Create one-time scheduled actions that raise the group's minimum and desired capacity at 08:30 on each exam date and lower them afterwards.
B. Add a predictive scaling policy in forecast and scale mode, so Auto Scaling learns the login pattern and launches instances ahead of it.
C. Add a warm pool of stopped, pre-initialised instances to the group, so that instances launched by the scaling policy enter service faster.
D. Lower the target tracking policy's CPU target from 60% to 30%, so that the group keeps more spare instances running all the time.

Show the answer and explanation

Answer: A

A. Right: Correct. Scheduled actions can run once at a set date and time, so the group can be scaled out before the known 09:00 login rush and scaled back in after the exam. The target tracking policy still handles any load above the scheduled capacity. Learn more: Scheduled scaling for Amazon EC2 Auto Scaling (opens in a new tab)
B. Wrong: Predictive scaling forecasts load from recurring daily and weekly patterns in up to 14 days of history. Exams on irregular dates do not form such a pattern, so the forecast would not reliably add capacity before 09:00. Known one-off dates suit scheduled actions. Learn more: How predictive scaling works (opens in a new tab)
C. Wrong: A warm pool shortens the time to bring an instance into service, but instances only leave the pool when the scaling policy scales out. That happens after CPU rises at 09:00, so capacity is still added after the rush has started rather than before it. Learn more: Decrease latency for applications with long boot times using warm pools (opens in a new tab)
D. Wrong: A lower target keeps extra instances running every day, which costs more on the many days without exams. It is still reactive, so a sudden jump of thousands of logins can outrun the spare capacity while new instances take 8 minutes to start. Learn more: Target tracking scaling policies for Amazon EC2 Auto Scaling (opens in a new tab)

Explanation

The load spike is known in advance but does not repeat on a regular schedule, and instances take 8 minutes to become ready. One-time scheduled actions put capacity in service before 09:00 on each exam date. Predictive scaling needs a recurring pattern, and warm pools and lower targets still react only after the load arrives.

SAA-C03 practice question: EC2 Auto Scaling (2 of 3)

Explanation

Study

Keep practising