Elasticache

1. AWS Elasticache is an in memory cache based db for AWS cloud. Fully managed, easy to deploy, operate and scale as per customers needs
2. Reduces the disk access by saving the most used and most critical data in the memory thus reduces latency
3. Supports two popular cacheing engines
4. Memcached
   1. Not persistent, memory only
   2. Port (11211)
   3. Parameter Group: acts as a container for engine configuration values that can be applied to one or more clusters. 
   4. node type (Eg: cache.r4.large or cache.t2.small)
   5. Specify security groups, subnets (for assigning private ips to nodes)
   6. Specify upto 20 nodes in your cluster. A node is a partition of your data.
5. Redis is a in memory key-value store (persistent db) that supports structured data sets such as lists, tables. Redis can be used as db, cache and message broker
   1. Cluster mode is optional
   2. Port 6379
   3. parameter group
   4. node type (Eg: cache.r4.large or cache.t2.small)
   5. number of shards. A shard is a partition of your data and is comprised of one primary and up to five read replicas
   6.  number of replicas per shard
   7. Multi AZ with auto failover
   8. Encryption at rest/transit
   9. Backups
6. For saving web server sessions, use AWS Elasticache (Better than DynamoDB)
7. Elasticache can be used to
   1. Reduce load on web server, application tier
   2. Game leaderboards Redis sorted lists
   3. Messaging (Redis pub/sub)
   4. Recommendations (Redis counters & hashes)