SAA-C03 Design Cost-Optimized Architectures Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Use On-Demand Instances because interruptions are not allowed for production workloads.

  Why it's wrong here

  On-Demand Instances eliminate the risk of EC2 interruptions because you pay a higher, per-second rate for guaranteed capacity, but AWS does not forbid production workloads from using interrupting instances. The real constraint is application resilience: if the thumbnail job uses checkpointing to S3 or a shared filesystem, it can run on Spot even in production. Choosing On-Demand purely because 'production' implies no interruptions is incorrect and unnecessarily expensive for fault-tolerant batch processing.

  When this WOULD be correct

  For a production database with strict uptime SLAs and no tolerance for interruptions, On-Demand Instances would be the correct choice to ensure continuous availability.

• ✓

  Use EC2 Spot Instances, accepting the possibility of interruptions and using checkpoints to resume.

  Why this is correct

  EC2 Spot Instances offer spare compute capacity at discounts of up to 90% compared to On-Demand. Although AWS can reclaim capacity with a two-minute interruption notice, the thumbnail batch can be made resilient by checkpointing progress to Amazon S3 or Amazon EFS and resuming from the last completed step. Because image processing is idempotent and time-flexible, this provides the lowest cost without losing completed work.

• ✗

  Purchase Reserved Instances because they provide a discount regardless of the workload timing.

  Why it's wrong here

  Reserved Instances require a 1- or 3-year commitment and provide a discounted hourly rate only while an instance is running; if the batch job is short or sporadic, you still pay for the entire commitment even during idle time. Standard RIs are designed for predictable 24/7 or steady-state workloads, not for interruptible batch jobs that may run at irregular intervals. The discount is tied to a term, not to workload timing, so it can actually increase costs if the cluster is not continuously utilized.

• ✗

  Buy Savings Plans because they guarantee capacity and remove the risk of interruptions entirely.

  Why it's wrong here

  Savings Plans are a flexible pricing model that exchanges a committed hourly spend (1- or 3-year term) for lower compute rates, but they do not guarantee capacity or provide any protection against Spot reclamation. Even if Spot usage is covered under a Savings Plan, the underlying instances can still be interrupted by EC2 at any time. Additionally, committing to a Savings Plan for a batch workload that runs only occasionally means you pay for a fixed compute baseline whether or not the job is running.

  When this WOULD be correct

  A company has a steady-state workload (e.g., a web server running 24/7) and wants the lowest cost for that predictable usage, accepting a 1- or 3-year commitment. Savings Plans would be the best cost optimization choice.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.

Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

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