AWS Certified SysOps Administrator – Associate (legacy) — Question 616

A financial service company is running distributed computing software to manage a fleet of 20 servers for their calculations. There are 2 control nodes and 18 worker nodes to run the calculations. Worker nodes can be automatically started by the control nodes when required. Currently, all nodes are running on demand, and the worker nodes are used for approximately 4 hours each day.
Which combination of actions will be MOST cost-effective? (Choose two.)

Answer options

• A. Use Dedicated Hosts for the control nodes.
• B. Use Reserved Instances for the control nodes.
• C. Use Reserved Instances for the worker nodes.
• D. Use Spot Instances for the control nodes and On-Demand Instances if there is no Spot availability.
• E. Use Spot Instances for the worker nodes and On-Demand Instances if there is no Spot availability.

Correct answer: C, D

Explanation

Using Reserved Instances for the worker nodes (C) secures a predictable discount for the computing capacity required for daily calculations. Opting for Spot Instances with an On-Demand fallback for the control nodes (D) helps drastically lower the baseline cost of the management layer while ensuring the orchestration system remains operational.