AWS Certified SysOps Administrator – Associate (legacy) — Question 695
You run a web application where web servers on EC2 Instances are in an Auto Scaling group. Monitoring over the last 6 months shows that 6 web servers are necessary to handle the minimum load During the day up to 12 servers are needed five to six days per year, the number of web servers required might go up to
15.
What would you recommend to minimize costs while being able to provide hill availability?
Answer options
- A. 6 Reserved instances (heavy utilization). 6 Reserved instances {medium utilization), rest covered by On-Demand instances
- B. 6 Reserved instances (heavy utilization). 6 On-Demand instances, rest covered by Spot Instances
- C. 6 Reserved instances (heavy utilization) 6 Spot instances, rest covered by On-Demand instances
- D. 6 Reserved instances (heavy utilization) 6 Reserved instances (medium utilization) rest covered by Spot instances
Correct answer: B
Explanation
The baseline load of 6 EC2 Instances runs 24/7 and is best covered by Reserved instances (heavy utilization) to secure the lowest pricing for continuous usage. The daily daytime spike of 6 additional instances is highly predictable but does not run all day, making On-Demand instances the safest choice to guarantee availability without long-term commitment. The remaining 3 instances needed only 5 to 6 days a year represent a transient, non-critical peak that can be economically handled using Spot Instances to minimize idle capacity costs.