Glossary
Also: RI
Two ways to pay considerably less than on-demand rates in exchange for a one or three year usage commitment.
Reserved Instances commit to an instance type, Savings Plans to an hourly spend. Both save between 20 and 60 percent against list price, depending on term and upfront payment.
The decision is not technical but one about planning certainty: how much base load will still be there in a year.
How you notice it
Frequently asked
For most cases Savings Plans, because they commit to an hourly spend rather than an instance type and therefore survive rebuilds. Reserved Instances still pay off for databases, where the instance family stays stable anyway. Either way: rightsize first, then commit.