Amazon ElastiCache reserved nodes
Amazon ElastiCache reserved nodes give you the option to make a low, one-time payment for each cache node you want to reserve. In turn, you receive a significant discount on the hourly charge for that node. Amazon ElastiCache provides three reserved cache node types (Light Utilization, Medium Utilization, and Heavy Utilization) that enable you to balance the amount you pay up front with your effective hourly price. Based on your application workload and the amount of time you plan to run them, Amazon ElastiCache Reserved Nodes might provide substantial savings over running on-demand Nodes. Reserved Cache Nodes are available for both Redis and Memcached.
For more information, see Amazon ElastiCache reserved nodes.