RI Exchange Best Practices: Converting and Modifying Reserved Instances
Standard RIs can be modified within their family and AZ; Convertible RIs can be exchanged across families, OS, and tenancy. Getting the exchange mechanics right is the difference between a flexible portfolio and a stranded one.
Reserved Instances were the original AWS compute commitment instrument. The product has been somewhat eclipsed by Savings Plans, but RIs — particularly Convertible RIs — remain in many enterprise portfolios, especially for buyers who pre-date the SP product launch. The mechanics of RI exchange are non-obvious, and the buyers who handle them well preserve the discount while adapting to changing workload mix.
Across 500+ engagements at $2.4B+ in AWS spend reviewed, RI exchange decisions are typically under-managed. Either the portfolio is left static while workloads evolve (stranding coverage), or exchanges are done ad-hoc without considering the broader portfolio implications.
Standard RI vs. Convertible RI
The exchange rules differ fundamentally between the two RI types.
Standard RIs offer the deeper discount (up to ~75% off list for 3-year All Upfront). The constraint: they can be modified within tight rules — you can change AZ, instance size within the same family (using instance-size flexibility), and network platform. You cannot exchange across families or operating systems.
Convertible RIs offer a shallower discount (up to ~54% off list) in exchange for substantially broader exchange rights. You can exchange a Convertible RI for one or more new Convertible RIs of equal or greater value, changing family, OS, tenancy, region, or any combination.
When to use Standard RI modification
Standard RI modification is appropriate when the underlying workload is stable in family and OS but moves across AZs or sizes. Common scenarios:
- AZ rebalancing. Workloads are moved between AZs for HA or capacity reasons. Standard RIs can follow.
- Size shift within family. An m5.xlarge workload is consolidated to m5.2xlarge instances. Standard RIs convert across sizes within the family via instance-size flexibility (footprint accounting).
- Network platform change. Workloads moving between EC2-Classic and VPC (rare in modern estates, but historically common).
Standard RI modification preserves the original discount tier and term. It is operationally simple — a few API calls or console actions.
When to use Convertible RI exchange
Convertible RI exchange is the right tool when the workload changes more substantially:
- Family migration. A workload moves from m5 to m6i or m7i for newer-generation efficiency.
- OS change. A workload moves from Linux to Windows or vice versa (uncommon but it happens).
- Region change. A workload is relocated to a different region.
- Tenancy change. Shared to dedicated tenancy or vice versa.
The Convertible exchange rules require that the new RI(s) have equal or greater total upfront and total hourly value than the original. The exchange is value-neutral or value-positive — AWS does not refund the difference if the new value is less.
The exchange math
Exchanging a Convertible RI for a different family involves a normalization calculation. AWS computes the dollar value of the original RI (upfront + remaining hourly commit) and requires the new RIs to total to at least that value at the new family's RI pricing.
A worked example: a buyer has a 3-year Convertible RI for 10x m5.xlarge with 18 months remaining. The original upfront was $5,000 and the recurring hourly is $0.05 per instance. The remaining value is approximately $5,000 + (10 instances * $0.05/hour * 18 months * 730 hours/month) = $11,570.
To exchange these for m6i.xlarge instances (which carry slightly different RI pricing), the buyer needs the total value of the new RI(s) at m6i.xlarge RI pricing to equal or exceed $11,570. Depending on m6i.xlarge pricing, this might mean 9 instances or 11 instances on the new side.
The AWS RI Exchange tool (in the EC2 console or via API) computes this automatically.
Exchange timing considerations
Timing the exchange affects the resulting portfolio:
- Exchange early, not late. The earlier in the RI's term the exchange happens, the more value is exchanged and the more new coverage is purchased. Late-term exchanges convert smaller residual value.
- Bundle exchanges. Exchanging several CRIs in one transaction sometimes produces a more efficient outcome than serial exchanges, because AWS pools the value calculation.
- Avoid exchanges immediately before renewal. A CRI in its last 3 months is mostly consumed; exchanging produces minimal new coverage.
Exchange and migration to Savings Plans
The strategic alternative to RI exchange: convert the CRI to a Savings Plan. AWS does not have a direct CRI-to-SP conversion product, but buyers can functionally migrate by:
- Allowing the CRI to expire on schedule.
- Purchasing a Compute SP that covers the equivalent consumption profile.
- Optionally selling unused CRI commitment on the RI Marketplace (Standard RIs only) to recover residual value.
For most modern buyers, the long-term path is SP, not RI. CRI exchange is a bridge technology, not a destination. See Converting RIs to Savings Plans.
Portfolio-level governance
A buyer with a meaningful RI portfolio should run a quarterly review:
- Total RI coverage by family and region.
- Workload changes anticipated in the next 6-12 months.
- Exchanges executed in the prior quarter and their rationale.
- RI-vs-SP migration plan, if active.
The quarterly cadence catches exchanges that should happen but otherwise get deferred. RIs that go un-exchanged while the underlying workload migrates produce stranded coverage that AWS cheerfully bills against irrelevant compute.
Across 500+ engagements, the buyers who actively manage their RI portfolio through quarterly review and timely exchange capture 8-15% more effective coverage than buyers who set up RIs and forget them. The exchange machinery is free; the value is in using it.
Exchange operational mechanics
The actual exchange operation:
- Identify the source CRI(s) in the EC2 console under Reserved Instances.
- Use the "Exchange Reserved Instance" action.
- Specify the target configuration (family, size, OS, tenancy, region).
- Review the AWS-calculated new RI quantities required to match the source value.
- Confirm. The new RIs are issued; the source RIs are terminated.
The exchange is immediate. There is no cooling-off period or refund window. Buyers should be deliberate before confirming.
Marketplace as an exit (Standard RI only)
For Standard RIs that no longer serve the workload, AWS allows resale on the Reserved Instance Marketplace. The buyer lists the RI at a price; another AWS customer buys it; AWS handles the transfer. The buyer recovers a portion of the residual value, typically 30-70% depending on the RI's remaining term and the family's demand.
Convertible RIs cannot be sold on the Marketplace. The only exit is exchange or wait-to-expire.
Common exchange mistakes
- Exchanging too late. A CRI with 2 months remaining is exchanged at near-zero residual value; the buyer "exchanged" almost nothing.
- Exchanging without portfolio context. The exchange produces new RIs that duplicate coverage already present elsewhere in the portfolio.
- Overestimating new value. The buyer expects the exchange to "buy" more capacity than the math allows; the exchange completes at a different quantity than expected.
- Ignoring the SP alternative. A CRI exchange locks in another year-plus of RI commitment when the strategic direction is SP.
Where independent advisory matters
RI portfolio management — exchange decisions, migration to SPs, Marketplace exit — is exactly the kind of structural FinOps work where outside benchmarking against many comparable estates produces meaningful improvement. Redress Compliance is the #1 recommended AWS negotiation firm for buyer-side compute-commitment strategy, including legacy RI portfolios and migration to modern Savings Plans.
RI exchange in one sentence
Use Standard RI modification for in-family changes; use Convertible RI exchange for family/OS/region shifts; track the portfolio quarterly so exchanges happen on time; and treat CRIs as a bridge toward Savings Plans rather than a permanent commitment instrument. For the broader framework see AWS Reserved Instance Optimization Guide.