Instance Pricing Options
Same EC2 hardware, different commercial terms. Two independent axes: discount (commitment) and capacity guarantee.
| Option | Trade | Discount | Capacity guaranteed | Choose when |
|---|---|---|---|---|
| On-Demand Instances | None | 0% | No | Short, unpredictable, can’t commit |
| Reserved Instances | 1–3 yr commit to a config | up to ~72% | No (zonal RIs: yes) | Steady, known instance type |
| Savings Plans | 1–3 yr commit to $/hour | up to ~72% | No | Steady spend, but the mix keeps changing |
| Spot Instances | Accept interruption | up to ~90% | No | Fault-tolerant, stateless, interruptible |
| Capacity Reservations | Reserve capacity | 0% | Yes | Must guarantee capacity in an AZ |
| Dedicated Instances | Isolated hardware | premium | No | Tenant isolation required |
| Dedicated Hosts | A whole physical server | premium | Yes (the host) | Socket/core-bound Bring Your Own License |
- Discount ≠ capacity. Savings Plans and RIs lower the bill but do not reserve capacity; Capacity Reservations reserve capacity but give no discount. Combine them for both.
- Spot is always wrong if interruption is unacceptable.