GlossaryCommitments

What Is a Reserved Instance? AWS Reservations, Explained

A Reserved Instance is a billing discount, not a physical server: commit to an instance family for one or three years and pay up to 72 percent less.

Erik LoydMay 27, 20262 min read

Reserved Instance

A Reserved Instance is a billing discount, not a physical server: commit to an instance family for one or three years and pay up to 72 percent less.

Related termssavings plan

A Reserved Instance is a discount applied to usage that matches a description, not a specific machine you own. You commit to an instance configuration, for example m7i instances in us-east-1 for one year, and any running instance that matches those attributes bills at the reserved rate instead of the on-demand rate. Stop the matching instances and the discount sits idle, but you keep paying for the reservation.

The two kinds

Standard RIs hold their attributes for the full term and carry the deepest discount, up to 72 percent off on-demand for a 3-year all-upfront EC2 reservation. If your needs change mid-term, the one exit is the AWS Marketplace, where standard EC2 RIs can be listed and sold to other customers.

Convertible RIs can be exchanged during the term for a reservation with different attributes, a different family, OS, or tenancy, as long as the new reservation is of equal or greater value. The flexibility costs several points of discount, and exchanges are a manual process rather than an automatic one.

Scope: regional or zonal

A regional RI applies anywhere in the region, and for Linux instances with shared tenancy it flexes across sizes within the family: one m7i.2xlarge reservation covers two m7i.xlarge instances through what AWS calls instance size flexibility. A zonal RI pins to one availability zone and gives up that flexibility in exchange for a capacity reservation, a guarantee the instances can actually launch there.

Beyond EC2

The reservation model is the only commitment discount for most AWS databases. RDS, ElastiCache, OpenSearch, and Redshift each sell reserved nodes or instances on the same one-or-three-year, up-to-around-60-percent pattern, and none of them are covered by Savings Plans. This is why reservations remain relevant even for teams that buy Savings Plans for all their compute.

Reserved Instance or Savings Plan?

For EC2 itself, Savings Plans have largely replaced RIs: a Compute Savings Plan follows workloads across families and regions automatically, where a standard RI strands and a convertible RI needs a manual exchange. The reservation's remaining advantages are the marketplace exit, the zonal capacity guarantee, and everything that is not EC2.

How the two instruments compare purchase by purchase, and how to size either one, is covered in our commitments research.

Reserved InstancesCommitmentsEC2RDS

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