Aurora Commitment Pricing — Mechanics Deep Dive
Reserved Instances (RI)
RIs are a per-instance commitment for provisioned Aurora. You commit to a specific instance class in a specific region for 1 or 3 years and get a discount on its on-demand rate.
Payment Options
| Option | Upfront | Recurring | Term | Discount ceiling |
|---|---|---|---|---|
| No Upfront | $0 | Monthly fee | 1yr only | up to ~30% |
| Partial Upfront | ~50% of term | Lower monthly | 1 or 3yr | up to ~63% (3yr) |
| All Upfront | Full term cost | $0 | 1 or 3yr | up to ~66% (3yr) |
These are AWS-published ceilings (the up-to maxima). The per-scenario estimates in mechanics.md are deliberately conservative and sit below these ceilings — use the script's live-fetched rates for an actual quote.
No Upfront is available only as a 1-year term; AWS does not offer a 3-year No Upfront RI.
Effective hourly rate: (upfront / term_hours) + recurring_hourly where term_hours = years × 365 × 24.
Size Flexibility
An RI for one instance size in a family covers equivalent normalized units of other sizes. Example:
- 1×
db.r7g.2xlargeRI can cover 2×db.r7g.xlargeOR 4×db.r7g.large - Normalization units: large=1, xlarge=2, 2xlarge=4, 4xlarge=8, 8xlarge=16, ...
Size flexibility does NOT apply across families or generations. An r7g RI doesn't cover r8g, r6g, or m7g.
What RI Doesn't Cover
- Aurora serverless (ACU pricing)
- Storage or I/O requests (no RI for storage in Aurora)
RIs do cover Aurora I/O-Optimized compute, but each I/O-Optimized instance consumes 1.3x the normalized RI units of the equivalent Aurora Standard instance. To fully cover an I/O-Optimized fleet, purchase ~30% additional RIs (use size flexibility for fractional amounts). Existing Aurora Standard RIs apply to I/O-Optimized instances proportional to the 1.3x consumption.
Database Savings Plans (DSP)
DSP is a $/hour account-wide commitment. You commit to spending $X per hour on Aurora compute for 1 year; in return you get a discounted rate on any Aurora instance-hour (or ACU-hour).
Key Properties
- Only 1-year term — no 3-year DSP
- Covers ALL Aurora compute: provisioned + Aurora serverless + I/O-Optimized premium
- Family-agnostic: one DSP covers r7g, r8g, c7g, etc. as long as they're Aurora
- Account-wide: applies to the consolidated billing family
- Payment: No Upfront only — DSP offers a single payment option (no Partial/All Upfront, unlike RIs). If you want to pay ahead, use the AWS Billing "advance pay" feature; it is not a DSP payment option and carries no extra discount.
Coverage Limits
DSP only covers latest-gen instance families: r7g, r7i, r8g, r8gd, m7g, c7g, and similar. Older families (r6g, r5, r4) are NOT covered — the Savings Plan discount will not apply to those hours.
If your fleet runs on r6g, you have two choices:
- Migrate to r7g or newer before buying DSP (recommended — same $/GiB memory, better price/performance)
- Buy RIs for the r6g instances instead
Typical Discount
1yr DSP discount vs on-demand depends on deployment type: up to ~20% for provisioned instances and up to ~35% for serverless (the 35% headline is the serverless ceiling). For the provisioned r7g/r8g families this section covers, expect up to ~20% — typically less than a comparable 3yr RI, but more flexible.
Mutual Exclusion
Only one discount applies per instance-hour. Priority:
- RI coverage is applied first (to matching instances within that family)
- DSP then applies to any remaining Aurora usage (if hourly commitment not yet consumed)
- Anything above your DSP commitment bills at on-demand
You can mix RI + DSP strategically — e.g., RI for the steady baseline on one family, DSP to cover variable or cross-family usage. But the analyzer in this skill shows them as alternatives for clarity.
Break-Even Considerations
RIs save money when the instance runs more than ~40-60% of the term. Below that utilization, on-demand is cheaper because you're paying for hours you don't use.
- 1yr No-Upfront: break-even around 50% utilization
- 3yr All-Upfront: break-even around 40% utilization (but you front the cash)
If you're planning to migrate, upgrade, or shut down the cluster within the term, the commitment often costs more than on-demand.
I/O-Optimized Interaction
On I/O-Optimized clusters, compute is charged at 1.30× the standard rate. RI coverage applies to I/O-Optimized compute, but I/O-Optimized draws down RI normalized units 1.3x faster than Aurora Standard. To fully cover an I/O-Optimized cluster, buy ~30% more RIs (e.g., 10 db.r6g.large RIs → 13 needed → buy 3 more).
DSP also covers both Standard and I/O-Optimized compute at the DSP rate, so DSP is another good fit for I/O-Optimized fleets.
Multi-AZ and Failover
RI/DSP cover the writer and reader instances. Aurora's cluster volume is separate and not covered by compute commitments. Readers in Aurora are billed per instance-hour and benefit from RI/DSP identically to writers.
Aurora serverless Pricing
- RIs: not applicable
- DSP: covers ACU-hours for Aurora serverless
- DSP discount on ACU-hours is up to ~35% — typically LARGER than the up-to-20% discount on provisioned instances, making DSP especially valuable for serverless fleets
If a workload is truly variable (auto-pausing, scale-to-zero), DSP may not save money because you're committing to hourly $/hr even when the cluster is paused.
