AWS Savings Plan Service:

Savings Plan is a new commitment for discount model that applies up to 72 percent discount (vs on demand) on Amazon EC 2 and AWS Fargate usage They are much
more flexible than Reserved Instances, illustrated in the table below.

AWS-Savings-Plan

 

Similar to RIs, Savings Plans come in 1 year or 3 year terms, the commitment in each hour cannot be saved to be used in the next hour if no matching no demand instances were running, and will first apply benefits to resources in the account it was purchased in then share any remaining benefits with other linked accounts Different to RIs, Savings Plans discounts will first apply to on demand resources with the highest discount and they apply automatically to matching resources without manual work This automatically applied flexibility allows customers to purchase Savings Plans before waiting for other cost optimization work (e g right sizing) to complete.

AWS-Savings-Plan2

Services that should still use RIs for a discount are…
•Amazon RDS
•Amazon Redshift
•Amazon ElastiCache
•Amazon Elasticsearch
•Amazon DynamoDB
•Amazon CloudFront