Question: Is AWS ElastiCache Distributed?

Answer

Yes, AWS ElastiCache is distributed. ElastiCache supports two popular in-memory caching engines, Redis and Memcached, both of which offer distributed caching capabilities.

Redis

ElastiCache for Redis supports partitioning data across multiple nodes using a technique called sharding. This allows you to distribute the cache's data across a cluster of nodes, providing increased capacity and improved performance. To set up a sharded Redis cluster, you can create a Redis replication group with multiple shards (also known as node groups). Each shard consists of one primary node and one or more replicas.

Here's an example using AWS CLI to create a Redis cluster with 2 shards and 1 replica per shard:

aws elasticache create-replication-group \
    --replication-group-id my-redis-cluster \
    --replication-group-description "My sharded Redis cluster" \
    --num-node-groups 2 \
    --replicas-per-node-group 1 \
    --cache-node-type cache.t3.small \
    --engine redis \
    --engine-version 6.x \
    --cache-parameter-group default.redis6.x \
    --cache-subnet-group-name my-cache-subnet-group

Memcached

ElastiCache for Memcached also supports a distributed architecture by distributing data across multiple nodes. Each node behaves as an independent cache server, so there is no built-in data replication like in Redis. However, this allows you to easily scale your cache horizontally by adding or removing nodes on demand.

Here's an example using AWS CLI to create a Memcached cluster with 3 nodes:

aws elasticache create-cache-cluster \
    --cache-cluster-id my-memcached-cluster \
    --cache-node-type cache.t3.small \
    --engine memcached \
    --engine-version 1.5.16 \
    --cache-parameter-group default.memcached1.5 \
    --num-cache-nodes 3 \
    --cache-subnet-group-name my-cache-subnet-group

In conclusion, AWS ElastiCache is indeed distributed, enabling horizontal scaling and improved performance for both Redis and Memcached caching engines.