What is ElastiCache for Redis?

ElastiCache is a web service that makes it easy to set up, manage and scale a distributed in-memory data store or cache environment in the cloud.
Features:
- Automatic detection of and recovery from cache node failures
- Multi-AZ for a failed primary cluster to a read replica in Redis cluster
- Redis (cluster mode enabled) supports partitioning your data across up to 500 shards
ElastiCache works with both the Redis and Memcached engines.

Comparing Memcached and Redis

Redis supports:
- Multi-AZ with Auto-Failover
- Read replicas
- data durability using AOF persistence
- Backup and restore feautres
- Supports sets and sorted sets
  - Sorted sets guarantees both uniqueness and element ordering. Useful when creating something like a gaming leaderboard. Each time a new element is added, its ordered automatically.
- Supports IAM for authentication
Memcached support:
- None of what Redis supports
- Supports SASL based authentication

Users enter a token (password) on a token-protected Redis server.
Include the parameter --auth-token (API: AuthToken) with the correct token to create the replication group or cluster.
Key Parameters:
- --engine - Must be redis
- –engine-version - Must be 3.2.6,4.0.10 or later
- –transit-encryption-enabled - Required for authentication and HIPAA eligibility
- –auth-token - Required for HIPAA eligibility. This value must be correct token for this token-protected Redis-server
- –cache-subnet-group - Required fro HIPAA eligibility