AWS ElastiCache

AWS ElastiCache

• Querying a database will always be slower and more expensive than locating a key in a key-value pair cache.
• In-memory key-value store is to provide ultra-fast latency
• Most data stores have areas of data that are frequently accessed but seldom updated.
• It is an AWS fully managed web service
• In-memory key value data store in the AWS cloud
• It improves the performance of web applications by allowing for the retrieval of information from a fast, managed, in-memory system (instead of reading from the DB itself)
• Improves response times for user transactions and queries
• Can enhance response time for read-intensive or compute-intensive workloads
• It offloads the read workload from the main DB instances (less I/O load on the DB)
• If an Elasticache node fails, it is automatically replaced by AWS Elasticache Service
• Your application connects to your cluster using endpoints. An endpoint is a node or cluster’s unique address
• A cluster can have one or more nodes included within
• A cluster is a collection of one or more nodes using the same caching engine
• A cluster can be as small as one node
• Supports two caching engines:
  • Memcached
  • Redis

ElastiCache – Memcached

• Memcached is an easy-to-use, high-performance, in-memory data store.
• Cache or Session store
• It offers a scalable, open-source solution for delivering sub-millisecond response times
• Memcached is a popular choice for powering real-time applications in
  • Web and Mobile Apps
  • Gaming
  • Ad-Tech
  • E-Commerce.
• Storage is not persistent
  • Can not be used as a data store. If the node fails, the cached data (in the node) is lost
  • If the node restarts, data is lost
• Ideal front-end for data stores (RDS, DynamoDB…etc)
• Use cases:
  • Cache contents of a DB
  • Cache data from dynamically generated webpages
  • Transient session data
  • High frequency counters for admission control in high volume web Apps
• Does not support
  • Multi-AZ failover
  • Replication
  • Snapshots

Amazon Elasticache – Redis

• Built on open-source Redis and compatible with the Redis APIs
• Is persistent – snapshot can be taken
• At any time, you can restore your data by creating a new Redis cluster
  • Supports Redis master/slave replication
  • Supports snapshots (automatic and manual) to S3
  • You can copy your snapshots to other AWS regions
• Use cases:
  • Web and Mobile Apps
  • Healthcare Apps
  • Financial Apps
  • Gaming, Ad-Tech, and IoT
• Multi-AZ is done by creating read replica(s) in another AZ in the same region
• Clustering mode disabled:
  • Your Redis cluster can have only one shard
  • One shard can have one read/write primary node and 0-to-5 read only replicas
  • You can distribute the replicas over multiple AZs in the same region
  • Replication from the primary node to the read replica is asynchronous
  • Applications can read from any node in the cluster, but can write to the primary node only
• Clustering mode enabled:
  • Your Redis cluster can have up to 15 shards,
  • With the data partitioned across the shards
  • Each shard has one primary node and –5 read only replicas
  • Snapshots can slow down your nodes, better take snapshots from the read replicas

ElastiCache – Redis vs Memcached

Redis	Memcached
Multi AZ with Auto-Failover	Multi-node for partitioning of data (sharding)
Read Replicas to scale reads and have high availability	Multi-threaded architecture
Persistence	Non persistent
Backup and restore features	No backup and restore