Question: Is ElastiCache stateless?

Answer

ElastiCache is a fully managed in-memory data store service provided by AWS, which supports popular open-source caching engines such as Redis and Memcached. ElastiCache itself is a stateful service, which means it manages and maintains the state of the cache cluster nodes. However, the nodes within an ElastiCache cluster can be considered stateless.

When a client sends a request to an ElastiCache node, the node retrieves the requested data from its memory and returns it to the client. The data is not stored on the node permanently, but only cached temporarily in memory for faster access. If the node fails or is terminated, the data is lost and must be retrieved again from the original data source.

In this way, the nodes within an ElastiCache cluster are stateless with respect to the cached data. However, they still maintain state information about themselves and the cluster, such as their configuration and membership status.

Here's an example of how to get data from an ElastiCache Redis cluster using the Redis Python library:

import redis

# create a Redis client object
redis_client = redis.Redis(host='my-elasticache-cluster.abc123.use1.cache.amazonaws.com', port=6379, db=0)

# set a key-value pair
redis_client.set('mykey', 'myvalue')

# retrieve the value by key
value = redis_client.get('mykey')
print(value)  # b'myvalue'

In the above code, we create a Redis client object and connect it to an ElastiCache Redis cluster. We then set a key-value pair and retrieve the value by key. Because the data is cached in-memory, the retrieval operation is fast and efficient.