SAA-C03 Q28 · Cost

Question

A company runs a production application on a fleet of Amazon EC2 instances. The application reads the data from an Amazon SQS queue and processes the messages in parallel. The message volume is unpredictable and often has intermittent traffic. This application should continually process messages without any downtime. Which solution meets these requirements MOST cost-effectively?

Accepted Answer

**Answer D: Reserved Instances (baseline) + On-Demand Instances (additional capacity)**

Let's map each requirement to the solution:

1. **'Continually process messages without any downtime'** → This is the critical constraint. The application CANNOT tolerate interruptions. Reserved Instances provide guaranteed, always-available capacity for the baseline workload. On-Demand Instances also provide guaranteed capacity — they are never interrupted by AWS.

2. **'Unpredictable and intermittent traffic'** → There is a steady baseline of work (messages always flow, just volume varies), plus unpredictable spikes. Reserved Instances cover the baseline cheaply. On-Demand Instances elastically handle spikes without capacity risk.

3. **'MOST cost-effectively'** → Reserved Instances offer up to 72% d

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🏗️ Architecture

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💰 Cost

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