Pricing for AWS ElastiCache depends on various factors such as instance type, region, and whether you're using reserved instances or on-demand pricing. However, it's important to note that the choice between Redis and Memcached does not directly impact the price - both are priced the same if you're comparing identical resources (like memory, CPU).
Here's how AWS ElastiCache is generally priced:
On-Demand Instances: Pay for compute capacity by the hour with no long-term commitments. This enables you to increase or decrease your compute capacity depending on the demand of your application and only pay the specified hourly rate.
Reserved Instances: This provides you with a significant discount (up to 75%) compared to On-Demand instance pricing. You have the flexibility to change families, operating system types, and tenancies while benefiting from Reserved Instance pricing when you use Convertible Reserved Instances.
Data Transfer: There might be costs associated with data transfer, particularly when transferring data between AWS regions or out of AWS.
It's noteworthy that ElastiCache also offers a Free Tier that allows you to explore the service at no upfront cost.
To make an informed decision about which option (Redis or Memcached) suits your needs better, consider their features rather than pricing. For example, Redis supports a richer set of data types (e.g., lists, sets), has built-in replication, and offers persistence, whereas Memcached might be easier to use in simple key-value cache scenarios.
Make sure to always check the most up-to-date pricing from the official AWS pricing page for ElastiCache.