Amazon ElastiCache

• ElastiCache is a web service
• Used to set up, manage, and scale distributed in-memory cache environments in AWS.
• Provides a high performance, resizable, and cost-effective in-memory cache
• Removes complexity associated with deploying and managing a distributed cache environment.
• Works with the Redis and Memcached engines
• By default, the AWS SDKs, AWS CLI, ElastiCache API, and ElastiCache console reference the US-West (Oregon) region.

ElastiCache Node

• Node is the smallest building block in Elasticache
• Node can exist in isolation from
• Node can be in some relationship to other nodes.
• It is a fixed-size chunk of secure, network-attached RAM.
• Each node runs an instance of the engine and version that was chosen during cluster creation.
• Scale the nodes in a cluster up or down to a different instance type.

ElastiCache operations for clusters:

• Creating a cluster
• Modifying a cluster
• Taking snapshots of a cluster (all versions of Redis)
• Deleting a cluster
• Viewing the elements in a cluster
• Adding or removing cost allocation tags to and from a cluster

Redis

Redis, expands to Remote Dictionary Server

• It is a fast, open-source, in-memory key-value data store
• Can be used as
  • a database
  • cache
  • message broker
  • queue
• The project started by Salvatore Sanfilippo, to improve scalability of his Italian startup.
• Redis delivers sub-millisecond response times
• Enables millions of requests per second
• Good for real-time applications in
  • Gaming
  • Ad-Tech
  • Financial Services
  • Healthcare
  • IoT
• Popular choice for
  • Caching
  • session management
  • gaming
  • leaderboards
  • real-time analytics
  • geospatial
  • ride-hailing
  • chat/messaging
  • media streaming
  • pub/sub apps.

Redis in Brief

• All Redis data resides in-memory
• Hence, Redis avoid seek time delays
• Can access data in microseconds.
• Redis features
  • versatile data structures
  • high availability
  • geospatial
  • Lua scripting
  • Transactions
  • on-disk persistence
  • cluster support
  • simpler to build real-time internet scale apps.

Redis data types

• Strings – text or binary data up to 512MB in size
• Lists – a collection of Strings in the order they were added
• Sets – an unordered collection of strings with the ability to intersect, union, and diff other Set types
• Sorted Sets – Sets ordered by a value
• Hashes – a data structure for storing a list of fields and values
• Bitmaps – a data type that offers bit level operations
• HyperLogLogs – a probabilistic data structure to estimate the unique items in a data set

Redis Cluster and Shard

• A Redis shard (or a node group in the API and CLI) is a grouping of 1 to 6 related nodes.
• A Redis (cluster mode disabled) cluster always has one shard.
• A Redis (cluster mode enabled) cluster can have 1–90 shards.
• A multiple node shard implements replication by have one read/write primary node and 1–5 replica nodes.
• A Redis cluster is a logical grouping of one or more ElastiCache for Redis Shards.
• Data is partitioned across the shards in a Redis (cluster mode enabled) cluster.

AWS and Memcached

• Node is the smallest building block in Elasticache
• Each node runs an instance of Memcached.
• Can scale the nodes in a cluster up or down to a different instance type.
• The Memcached engine supports Auto Discovery, in which, client programs automatically identify all nodes in cache cluster, initiate and maintain connections to all of these nodes. No manual configuration.
• Client application connects to a configuration endpoint having DNS entry with CNAME entries for each of the cache node endpoints.
• Memcached is available in multiple AWS Regions around the world.

Choose Memcached if

• You need the simplest model possible.
• You need to run large nodes with multiple cores or threads.
• You need the ability to scale out and in, adding and removing nodes as demand on system increases and decreases.
• You need to cache objects, such as a database.