Glossary · Pricing & Commitments
What is a Reserved Instance?
An older AWS commitment model — pre-pay for a specific instance type / region / tenancy / OS for 1 or 3 years in exchange for a discount of up to ~72%.
By HabileLabs
Reserved Instance (RI)
A Reserved Instance (RI) is a billing concept (not a separate instance type) where you commit to a specific EC2 instance configuration — instance family, size, region, OS, tenancy — for 1 or 3 years. In exchange, AWS gives you a discount of up to ~72% off on-demand pricing for matching usage.
RIs come in Standard (highest discount, least flexible) and Convertible (can be swapped to different instance types mid-term, at a lower discount) variants. AWS positions Savings Plans as the more flexible successor for most new commitments — but RIs remain valid for the workloads they already cover, and for RDS, ElastiCache, OpenSearch, and Redshift where Savings Plans don't apply.
RIs still cover a large portion of long-running AWS spend in most accounts that have been operating for more than a year. The most common waste mode is RI mismatch: the RI is for an instance family you've stopped using, so its discount doesn't apply to anything. That waste is invisible on the bill — you only see the on-demand rate for the new workload plus the upfront RI charge.
Refine cross-references active RIs against running usage and flags mismatches before they accumulate into months of wasted commitment.
- !AWS auto-applies RI discounts to matching usage; you cannot manually assign one RI to one workload.
- !Standard RIs can be resold on the AWS RI Marketplace if you no longer need them; Convertible RIs cannot. Either way, lock-in is real.
- !For non-EC2 services (RDS, ElastiCache, etc.) RIs are still the only commitment option.
Related
Savings Plan
A 1- or 3-year AWS commitment to a steady level of compute usage ($/hour) in exchange for a lower rate. Flexible across instance family, size, OS, region, and tenancy.
Compute Savings Plan
The most flexible AWS Savings Plan variant — applies to EC2, Fargate, and Lambda usage across any region, instance family, OS, and tenancy.
Spot Instance
A spare EC2 capacity instance priced at up to ~90% off on-demand, with the trade-off that AWS can reclaim it with 2 minutes' notice.
Cost Optimization
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