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


AWS ElastiCache

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