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.
AA. 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.
BB. Add a predictive scaling policy in forecast and scale mode, so Auto Scaling learns the login pattern and launches instances ahead of it.
CC. Add a warm pool of stopped, pre-initialized instances to the group, so that instances launched by the scaling policy enter service faster.
DD. 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)
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.
Want more on EC2 Auto Scaling? The 5 full-length practice sets have 10 more EC2 Auto Scaling questions, 325 in all, none of them in the free exam. One payment of $14.99, no subscription. See the practice sets →