AWS EC2 On-demand capacity reservation is another new feature has been announced recently. This feature mainly focusing the customers who want to use a specific instance type on a particular availability zone for a long or short period. We just tried it and wanted to explain about how to use this properly.

Capacity Reservation:

First, we need to understand that this is to reserve the instance type for you, not RESERVED INSTANCES. In my past experience, while launching C4 family instance type on the us-east-1, it was showing the instance type is not available on this availability zone. So we changed the instance type for a web stack along with the autoscaling configurations. If this problem occurred during the autoscaling, then we may face an outage. This feature will solve this problem and you can reserve any instance type expect t2.nano

Where can we use this feature:

If you are running any massive batch workload on a particular time frame with high-end instance type, then you can think about this feature. (another choice is Spot instances, but im looking from the instance type perspective). You are re-deploying the entire stack from Cloudformation, and you are confident about the instance type then you can reserve the instance type before launching the stack and make the reservation until your next deployment. If you know any other use cases, please comment below.

Pricing:

Whenever you reserved the instance type, then you will be charged whether the instance has been launched or not. So once your reservation has done, launch your instances asap.

There is no additional price. AWS will be charged normal instance rate. If you have purchased RI, then it’ll be applied automatically.

Limitations: (from AWS Doc)

Active and unused Capacity Reservations count towards your On-Demand Instance limits.

Capacity Reservations can’t be shared across AWS accounts.

Capacity Reservations are not transferable from one AWS account to another.

Zonal RI billing discounts do not apply to Capacity Reservations.

Capacity Reservations can’t be created in Placement Groups.

Capacity Reservations can’t be used with Dedicated Hosts.

Reserve an Instance Type:

Go to AWS Ec2 console. Under the Instances section, you can see the Capacity Reservation.

2. Once you clicked the Create Capacity Reservation