Reserved Instances
The biggest discount in cloud billing has one silent failure mode.
Reserved Instances cut the cost of steady RDS, ElastiCache, and EC2 usage. They also end on a fixed date, and AWS does not renew them. Careful teams miss that date too. This guide shows how to catch it.
First, the basics
A Reserved Instance is a billing commitment.
You agree to pay for an amount of usage for 1 or 3 years. The usage is one instance class in one region. In return, you get a lower hourly rate than the on-demand price. AWS applies the discount to matching usage in your account automatically.
These are the discount ceilings in AWS published pricing. Your rate depends on instance class, term, and payment option.
Three payment options. Each changes how much you pay upfront.
EC2 has a second choice. Standard Reserved Instances give the deepest discount. They fix the instance attributes for the term. Convertible Reserved Instances give a smaller discount. You can exchange them for a different instance family, operating system, or tenancy during the term. RDS and ElastiCache have no convertible option. For those, the term and payment option are the only choices. Price your own choice with the free Convertible Check.
The part that catches people
The renewal cliff: RIs do not auto-renew.
AWS has no auto-renew feature for Reserved Instances. When a term ends, the instance keeps running. It does not restart, stop, or slow down. Only the price changes. Covered usage returns to the on-demand rate at once. It stays there until someone buys a new reservation. AWS sends no warning unless you turn on its alerts.
A lapse costs money from the first hour. These figures show the extra cost of one reservation on this instance.
- +$0.56after 1 hour
- +$13after 1 day
- +$134after 10 days
- +$403after 30 days
That is one reservation. Many terms end across a fleet in a given week, so the gaps add up. Use the savings calculator to estimate the cost with your own spend and days-late number. The Effective Savings Rate guide shows the same lapse as points off your fleet's savings rate.
Time the purchase with care. RDS and ElastiCache purchases start at once, so an early purchase bills next to the old reservation. An EC2 regional RI can be queued for its end date. See the queued purchase guide.
Why it slips
Nobody plans to miss a renewal. The process does not catch it.
End dates live in three consoles: RDS, ElastiCache, and EC2. They rarely sit next to the fleet they cover. Most teams track them in a spreadsheet that somebody set up once. A calendar reminder that nobody owns backs it up. A reservation's discount can also apply across the instance sizes in one family. So it gets harder to tell whether an RI still covers real usage each time the fleet changes shape. Fleets change constantly.
A practical checklist
Track every end date in one place
Keep one list with every reservation and every term end date. Memory and three separate consoles both drop dates.
Match reservations to what is running
A reservation with nothing to cover wastes money. The instance may have been resized, moved, or ended. Know which of your RIs cover real usage today.
Decide renew or lapse from current usage
Base the new purchase on what runs now. Last term's purchase is a poor guide. Fleets change generation and shape between terms.
Keep one coverage view
Cover every account you run. A gap you cannot see is a gap you miss. A single view makes the gap visible.
Want step one done today? Paste your owndescribe-reserved-* output into the Expiry Check. You get every end date back in seconds. It is free and nothing is uploaded. You can also download the whole calendar as .ics or CSV.
How this scales with you
The cliff is the same at every fleet size.
Watch plan, $0. A renewal 14 days late costs about $92. A spreadsheet works until its owner is out the week a term ends. With few reservations, one late date is easy to miss.
Autopilot plan, $149. A renewal 14 days late costs about $951. Fleet changes outrun the review cycle. Coverage decays between reviews, and nobody did anything wrong. More things change between calendar reminders.
Scale plan, $499. A renewal 14 days late costs about $6,904. Nobody tracks renewals by hand at this scale. One reservation looks too small to matter. Thousands of them add up to a large bill.
The price does not change with the number of reservations. It covers ten or ten thousand. Reserver never takes a cut of what you save. See pricing.
Where Reserver fits
What you can do today, and what comes next.
Reserver connects to your AWS accounts read-only. It scans every Reserved Instance you own next to what is running. That builds the single coverage view the checklist calls for. The expiry radar shows every end date across every connected account. The matching engine flags a reservation with nothing left to cover. You buy the renewal yourself in the AWS console. As a free backstop, switch on AWS's own opt-in Reservation Expiration Alerts. They email up to 10 recipients 7, 30, or 60 days before expiry, as the AWS documentation explains. Renewal autopilot building · M5 and notification delivery building · M3 are not built yet. See features, how it works, and the security model behind the read-only connection. To choose a coverage target, read the coverage playbook. To compare terms, use the free Term Check. Before you renew a database or cache reservation, check the engine version. AWS bills Extended Support on old versions, and the reservation does not discount it. If AWS credits pay part of your bill, see what a credit can and cannot pay before you pick a payment option. Coming from Azure or Google Cloud? See why this cliff is AWS-specific. The other two clouds handle renewal differently.
Do Reserved Instances renew automatically?
No. AWS does not auto-renew Reserved Instances for RDS, ElastiCache, or EC2. When a term ends, you must buy a new reservation yourself. If nobody does, the instance keeps running as before. AWS bills it at the on-demand rate from that moment.
What happens when an RI expires?
The running instance is not affected. It does not restart and has no downtime. Only the price changes. Usage that the reservation covered returns to on-demand billing at once. AWS sends no warning unless you turned on its alerts. The higher rate stays until a new reservation covers the usage.
Should I buy a 1-year or 3-year term?
It depends on instance class, payment option, and how long that family stays in your fleet. A 3-year term usually gives the deeper discount. It also commits you for longer. If a family has run in your fleet for years, the longer term usually wins. If a family is new or likely to change, a 1-year term carries less risk. Reserver shows 1-year and 3-year terms side by side for your own fleet. The free Term Check does the same math for one reservation.
Is tracking renewals worth it for only a few reservations?
Yes. Watch is free, so preventing the loss costs nothing. The median reservation in our AWS price data saves about $1,484 a year. Renew it 14 days late and you lose about $57. That is one reservation, so the loss is small. It is still money you keep at no cost.
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.