Reserved instances vs on-demand, how much do reservations save?

For Magento workloads on AWS / Azure / GCP, reservations save 30-55% over on-demand pricing for the same compute. The exact split:

• 1-year, no-upfront reservation: ~30% saving over on-demand.
• 1-year, all-upfront reservation: ~40% saving (you pre-pay the year).
• 3-year, no-upfront: ~45% saving.
• 3-year, all-upfront: ~55-60% saving (deepest discount but biggest commitment).
• Savings Plans (AWS): ~30-50% with more flexibility across instance families.

When to reserve:

• Baseline always-on instances (web tier, RDS primary, Redis primary), reserve at 3-year all-upfront if you’re confident you’ll still be on Magento + AWS in 3 years. ROI is positive at month 14.
• Auto-scaling tier (workers, async queue consumers), keep on-demand or use AWS Spot Instances at -70% (with the caveat that they can vanish).
• OpenSearch dedicated nodes, reserve. They’re always-on, expensive, and worth the discount.

Don’t reserve if you’re mid-migration, evaluating providers, or have less than 12 months of historical traffic data. The lock-in penalty is bigger than the saving.

The calculator output is on-demand pricing. Apply -35% mentally if you’re planning to reserve at 1-year, -50% for 3-year reservations.