Question: How many ElastiCache nodes do I need?

Answer

The number of ElastiCache nodes you need depends on your specific requirements, including your expected workload size, application performance goals, and budget.

There are two types of ElastiCache nodes available: Memcached and Redis. The following factors can help you determine the number of nodes you need for each type of node:

Memcached

• The amount of memory required by your workload
• The number of connections per second required by your workload
• The size of the objects in your cache
• The read/write ratio of your workload

Redis

• The amount of memory required by your workload
• The number of operations per second required by your workload
• The number of keys stored in your cache
• The read/write ratio of your workload

To estimate the number of nodes required, you can use the ElastiCache calculator provided by AWS. This tool allows you to input various metrics related to your workload, such as cache size and query rate, and it will recommend the optimal number of nodes to achieve your desired performance goals.

Here's an example using Memcached: Let's say you have a workload with an estimated 10,000 requests per second (RPS) and a maximum object size of 1 MB. You expect that each node should have approximately 50 GB of memory. In this case, you would need a cluster with at least 20 nodes to handle the entire workload.

Here's an example using Redis: For a workload with an estimated 50,000 RPS and a maximum key size of 256 bytes, you may need a cluster with up to 10 nodes, each having around 30 GB of memory.

Keep in mind that these are just general guidelines, and your specific workload may require more or fewer nodes than these examples. It's always a good idea to perform load testing and benchmarking with realistic data to determine the optimal number of nodes for your workload.