Guides
Get the most out of every reservation.
No listicles, no fluff. Long-form guides that teach you exactly how Reserved Instance pricing, terms, and renewals work, so nothing you already paid for goes to waste.
Reserved Instances
The AWS Reserved Instance renewal playbook
A Reserved Instance does not renew itself. A lapse costs money from the first hour. This guide shows the cost by the hour and by the day, and how to catch every end date.
Coverage
The Reserved Instance coverage playbook
Reserved Instances only save money if they're covering something real, and covering everything isn't the goal either. How to measure coverage, set a target, and keep it accurate as your fleet grows from a handful of reservations to thousands.
Savings
The AWS Reserved Instance savings playbook
Every Reserved Instance is the same bet: pay some or all of it now for a lower rate later. Term and payment option change that bet. Running the math pays for itself at any fleet size.
Comparison
Reserved Instances vs Savings Plans
Two different commitments, both sold as "reservations." An RI locks in an instance class. A Savings Plan locks in an hourly spend. The renewal cliff catches both in the same way.
Effective Savings Rate
Effective Savings Rate, explained
Coverage tells you what's reserved. ESR tells you what it's worth. Two fleets can share a coverage number and have very different ESRs. A renewal lapse, priced in ESR, pays for a year of Autopilot by itself.
Renewal Laddering
The Reserved Instance renewal ladder
A reservation's term ends on the clock, not the calendar, and if too many end in the same week or month, one missed renewal turns into several. What expiry concentration is, the target FinOps teams ladder against, and what to do about a fleet that's already clustered.
Multi-cloud
What each cloud does at term end
A habit learned on Azure is exactly backwards on AWS. Each cloud handles the end of a commitment term in its own way. We checked each one against the vendor's documentation. The guide prices the gap for a fleet that runs all three.
Multi-account
How AWS shares a Reserved Instance discount
AWS shares a reservation's discount with every account on the same consolidated bill, by default. What that means for a two-account startup and an AWS Organization with thousands of reservations, and why the account that benefits is often not the account that has to renew.
Renewal timing
Queue an AWS Reserved Instance purchase
AWS can queue an EC2 Reserved Instance purchase years ahead, but the console only lands it on a UTC midnight, and RDS and ElastiCache cannot be queued at all. What that costs in real hours, and why it matters more the more reservations you run.
Instance generations
Reserved Instances and old-generation hardware
AWS retires an instance family long before most Reserved Instance terms end. An EC2 Convertible RI can follow. A Standard RI, an RDS reservation, and an ElastiCache reservation cannot. What that costs, and how to see it coming across thousands of reservations.
Coverage drift
Reserved Instance coverage drift
A term that ends at least ends. Coverage drift does not. A reservation stops matching the instance it was bought for, and nothing in AWS raises an alert. The three causes, the seven dimensions behind them, and what one drifted reservation costs at 30, 90, and 180 days.
Purchase quotas
AWS caps how many Reserved Instances you can buy
Reserving 300 EC2 instances in one Region does not happen in one month. AWS caps new Reserved Instance purchases at 20 per Region and 20 per zone, counts instances not orders, and can block the purchase from paying off at all. RDS and ElastiCache cap reservations a different way.
Rightsizing
Check for idle capacity before you reserve it
A Reserved Instance is a bet that an instance keeps running the way it runs today. Get that wrong, and the term still runs its course. What a commitment locks in per service, what Reserver checks before you buy, and the one rule it will not break: no signal is never read as idle.
Extended Support
Extended Support: the fee RIs do not discount
A reservation lowers the instance price. It does not lower the Extended Support fee AWS adds to old database and cache versions. On a common database, the fee is bigger than the whole saving. The dates, the math, and what to check before a renewal.
AWS credits
Should you reserve while you have AWS credits?
Credits do not pay upfront fees, but they can pay the hourly rate of a reservation. Reserve the steady part with No Upfront, and the same credit lasts about a quarter longer. The rules, the math, and the expiry date to watch.
Multi-account
Which AWS accounts should you connect?
A large AWS organization holds many accounts, and most run no instances. Connect the ones that run RDS, ElastiCache, or EC2, and the one that buys reservations. Three example organizations show the plan each one needs.
Getting started
Buy your first Reserved Instance
How to buy the first Reserved Instance without a costly mistake. What must match, which term is low risk, where to click in each console, and why the end date goes on a calendar on purchase day.
ReferenceNew to the vocabulary? Start with the glossary, plain-language definitions of every term these guides use →Original researchWant the numbers behind the advice? The RI Discount Index computes median discount, sparse cells, and lapse cost straight from the AWS price list →More guides as we go: reservation math, term strategy, and what changes at enterprise scale. Want a specific one written? Join the waitlist and tell us.
Stop overpaying for a steady fleet.
Reserver is in early access. Join the list, and we will onboard you when we have capacity. Your first recommendation lands within minutes of connecting.