Question: How is pricing calculated for ElastiCache replicas?

Answer

Amazon ElastiCache follows an on-demand pricing model, which means you pay for compute capacity by the hour with no long-term commitments. For replicas, you pay for the hourly usage of each node – meaning, the price depends on the type and number of nodes you use.

ElastiCache supports two types of engines - Redis and Memcached. For Redis, in addition to primary nodes, you can have read replicas, which are essentially additional copies of your data that can handle read traffic and support high availability. You would pay for these replicas just as you do for primary nodes.

Here's an example of how this might look:

# let's say you select cache.r5.large instances for your replicas in the US East (N. Virginia) region

number_of_replicas = 2  # you decide to have 2 replicas
price_per_hour = 0.284  # price per hour for cache.r5.large instance

total_price_per_hour = number_of_replicas * price_per_hour

Your total cost would then be the total_price_per_hour multiplied by the number of hours you run the replicas.

Keep in mind prices vary by region and instance type. Also, data transfer and storage costs could apply. For instance, there could be costs associated with replicating data across regions or taking snapshots of your data.

For the most accurate pricing, refer to the official Amazon ElastiCache Pricing page.