Does RI purchase for RDS guarantee capacity reservation?

Question

1. Customers can purchase dedicated reserved capacity for EC2 which means the instance is guaranteed to be available, but I do not think you can do that for RDS.  Can you please confirm? DB engine is SQL Server.
2. Does buying a RDS reserved instance help with instance availability as customers with RIs get priority over on demand.

Accepted Answer

Via https://aws.amazon.com/rds/faqs/

> Q: Do reserved instances include a capacity reservation?
> 
> Amazon RDS reserved instances are purchased for a Region rather than
> for a specific Availability Zone. As RIs are not specific to an
> Availability Zone, they are not capacity reservations. This means that
> even if capacity is limited in one Availability Zone, reservations can
> still be purchased in the Region and the discount will apply to
> matching usage in any Availability Zone within that Region.

Answer

1. Yes [ODCR ](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-capacity-reservations.html)(On-Demand Capacity Reservation) capability  is not available on RDS today.

2. I did not come across any documentation indicating RI prioritized over On-Demand. The value of RI is in discounts

Does RI purchase for RDS guarantee capacity reservation?

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