Convertible vs standard reserved instances: which to buy

Quick answer

Standard reserved instances give the deepest discount but lock you to an instance family and offer limited changes; convertible reserved instances discount somewhat less but let you exchange them for a different instance type, family, OS, or tenancy during the term. Choose standard when your workload is stable and you are confident about the instance family for the full term; choose convertible when you expect to change instance types as your architecture evolves. In practice, many teams now prefer savings plans for even more flexibility, but where RIs fit, the choice is discount depth versus the freedom to change.

Reserved instances trade a one or three year commitment for a discount over on-demand pricing. AWS offers two flavors, standard and convertible, and the difference is a classic tradeoff: standard gives a bigger discount but less flexibility, convertible gives more flexibility for a smaller discount. Which one fits depends entirely on how stable you expect your workload and instance choices to be.

The core tradeoff

Dimension	Standard RI	Convertible RI
Discount depth	Deepest	Somewhat less
Change instance type/family	Very limited	Yes, via exchange
Change OS / tenancy	No	Yes, via exchange
Sell on marketplace	Yes	No
Best for	Stable, known workloads	Evolving architectures

A standard RI commits you to an instance family for the term, with only minor within-family changes allowed, in exchange for the maximum discount. A convertible RI lets you exchange it for a different type, family, OS, or tenancy (of equal or greater value) if your needs change, but the discount is a bit shallower. Both come in one and three year terms, with deeper discounts for three year and for larger upfront payment.

When to choose standard

Choose standard reserved instances when your workload is stable and you are confident about the instance family for the full term, a steady database, a baseline compute fleet you know will keep running on the same family. You capture the deepest discount, and if plans change you can sell unused standard RIs on the AWS Reserved Instance Marketplace. The catch is that if your instance needs shift and you cannot sell, you are stuck paying for capacity you no longer want.

When to choose convertible

Choose convertible when you expect your architecture to evolve, migrating to newer instance families, changing sizes, or shifting workloads, and you want the freedom to exchange without losing the commitment. The slightly smaller discount buys insurance against being locked into the wrong instance type. This flexibility matters most for younger or fast-changing systems where the right instance family a year out is genuinely uncertain.

The savings plans alternative

Since AWS introduced savings plans, many teams reach for them instead of RIs because they offer commitment discounts with even more flexibility (compute savings plans apply across instance families, sizes, regions, and even Fargate and Lambda). The tradeoff between commitment types is covered more fully alongside broader commitment strategy; the short version is that RIs still make sense for specific, stable capacity and where marketplace resale matters, while savings plans suit fleets that shift often. Whichever you choose, model the underlying compute against the resource catalog and revisit coverage as usage changes, the same discipline behind tracking unit cost and watching data transfer as separate line items.

FAQ

What is the difference between convertible and standard reserved instances?

Standard RIs give the deepest discount but lock you to an instance family with only limited within-family changes, and can be sold on the marketplace. Convertible RIs discount somewhat less but let you exchange them for a different instance type, family, OS, or tenancy of equal or greater value during the term, though they cannot be sold on the marketplace. The tradeoff is discount depth versus flexibility.

Which reserved instance type should I buy?

Choose standard when your workload is stable and you are confident about the instance family for the full term, capturing the deepest discount. Choose convertible when you expect your architecture to evolve and want the freedom to exchange instance types. Many teams now prefer savings plans for even more flexibility, but where RIs fit, it comes down to how certain you are about your instance needs.

Can you change a convertible reserved instance?

Yes. A convertible RI can be exchanged for one or more RIs of a different instance type, family, operating system, or tenancy, as long as the new reservations are of equal or greater value. This lets you adapt to architecture changes without losing your commitment, which is the main advantage over standard RIs at the cost of a slightly smaller discount.

Can you sell convertible reserved instances?

No. Standard reserved instances can be sold on the AWS Reserved Instance Marketplace if your plans change, but convertible RIs cannot be sold there. Instead, convertibles offer the exchange mechanism to swap for different instance types. So the exit strategy differs: sell for standard, exchange for convertible.

Are reserved instances or savings plans better?

It depends. Savings plans offer commitment discounts with more flexibility, compute savings plans apply across instance families, sizes, regions, and even Fargate and Lambda, so many teams prefer them for fleets that shift often. Reserved instances still make sense for specific, stable capacity and where marketplace resale matters. Both require committing to steady usage; the difference is how broadly the discount applies.

Does C3X price reserved instance savings?

C3X prices infrastructure from your Terraform against a live catalog, so it surfaces the on-demand cost of compute before deploy. Commitment purchasing (choosing between standard, convertible, and savings plans) is a runtime financial decision based on steady usage, which C3X complements by making the underlying resource cost visible so you know what you would be committing to.

What to do next

See your compute cost before you commit to a reservation. C3X reads your Terraform and prices your resources against a live catalog. Start with the quickstart.