# COST05-BP06 - Perform cost analysis for different usage over time

Best practice: COST05-BP06
Pillar: Cost Optimization
Source: https://wellarchitected.cloudvisor.eu/docs/cost-optimization/cost05-bp06.html

## Implementation guidance

When selecting services, analyze cost not just for current usage but across the
expected range of usage over time. A service that is cheapest at today's volume
may not be the most cost-effective as the workload grows, shrinks, or changes
its access pattern. Modeling cost across future usage scenarios prevents
selecting a service that becomes expensive at scale.

### Model usage over time

**Project usage scenarios**: Define low, expected, and high usage scenarios over
a meaningful time horizon, based on business forecasts and historical growth.

**Compare candidate services across scenarios**: For each candidate service or
configuration, estimate cost under each usage scenario rather than at a single
point. Include the effect of pricing models (on-demand, Savings Plans, Reserved
Instances, tiered pricing) that change unit cost as volume changes.

**Account for the full cost curve**: Consider how cost scales — linearly,
in steps, or with volume discounts — and identify break-even points where a
different service or pricing model becomes cheaper.

### Use the analysis to decide

**Select for the expected lifecycle**: Choose the service that is most
cost-effective across the realistic range of future usage, not only at launch.

**Re-evaluate as usage changes**: Revisit the analysis when actual usage
diverges from projections, and use it together with COST05's other best
practices to keep service selection cost-effective over time.

**Automate the modeling**: Use the AWS Pricing Calculator and your detailed CUR
data (queried in Amazon Athena — the AWS analytics service, not an internal
agent) to make the analysis repeatable.

## AWS Services to Consider

<div class="aws-service">
  <div class="aws-service-content">
    <h4>AWS Pricing Calculator</h4>
    <p>Model the cost of candidate services across multiple projected usage scenarios before committing.</p>
  </div>
</div>

<div class="aws-service">
  <div class="aws-service-content">
    <h4>AWS Cost Explorer</h4>
    <p>Analyze historical usage trends to inform realistic low/expected/high scenarios for future cost analysis.</p>
  </div>
</div>

<div class="aws-service">
  <div class="aws-service-content">
    <h4>Savings Plans &amp; Reserved Instances</h4>
    <p>Factor commitment-based pricing into the cost curve when usage is sustained and predictable.</p>
  </div>
</div>

## Related Resources

<div class="related-resources">
  <ul>
    <li><a href="https://docs.aws.amazon.com/wellarchitected/latest/framework/cost_select_service_analyze_over_time.html">AWS Well-Architected — COST05-BP06 Perform cost analysis for different usage over time</a></li>
    <li><a href="https://docs.aws.amazon.com/wellarchitected/latest/framework/cost-05.html">COST05: How do you evaluate cost when you select services?</a></li>
  </ul>
</div>