AWS Certified Solutions Architect Professional SAP-C02 Practice Question

The correct answer is to reconfigure the Auto Scaling group to use a mixed instances policy. This approach allows the use of both Spot Instances and On-Demand Instances across various instance types. For a stateless and fault-tolerant workload like video transcoding, Spot Instances are ideal as they offer discounts of up to 90% compared to On-Demand prices. Using a mixed instances policy that is flexible across multiple instance types (e.g., from the C, M, and R families) and Availability Zones increases the likelihood of acquiring Spot capacity and improves resilience against interruptions in any single Spot pool. This strategy provides the greatest cost savings while ensuring the workload can be completed.

Incorrect answers:

• Purchasing a Compute Savings Plan provides a good discount but is less cost-effective than Spot Instances for this type of interruptible workload. Savings Plans offer up to 66-72% savings for a commitment, whereas Spot savings can reach 90%. This option is better suited for stable, predictable workloads, not for maximizing savings on a fault-tolerant batch job.
• Only rightsizing the instances, while a valid cost-optimization technique, does not leverage the significant discounts available through different purchasing options. The savings from rightsizing alone would be much lower than those achieved by incorporating Spot Instances.
• Using a Spot Fleet with a single instance type is a risky strategy. While it uses cost-effective Spot Instances, relying on a single pool (one instance type in one AZ) makes the application vulnerable to interruptions if that specific Spot capacity becomes unavailable. A mixed instances policy is superior because it diversifies the request across multiple capacity pools, increasing availability.