Amazon ElastiCache Overview¶

• The same way RDS is to get managed Relational Databases the ElastiCache is to get a manged Redis or Memcached
• Caches are in-memory databases with really high performance, low latency
• Helps reduce load off of databases for read intensive workloads
• Helps make your application stateless
• AWS takes care of OS maintenence / patching, optimizations, setup, configuration, monitoring, failure recovery and backups.

Using ElastiCache involves heavy application code changes.

ElastiCache Solition Architecture - DB Cache¶

• Application queries ElastiCache, if not available, get from RDS and store in ElastiCache
• Helps relieve load in RDS
• Cache must have an invalidation strategy to make sure only the most current data is used in there.

ElastiCache Solution Architecture - User Session Store¶

• User logs into any of the application
• The application writes the session data into ElastiCache
• The user hits another instance of our application
• The instance retrieves the data and the user is already logged in.

ElastiCache - Redis vs Memcached¶

• Redis

  • Multi AZ with Auto-Failover
  • Read replicas to scale reads and have high availability
  • Data Durability using AOF persistence
  • Backup and restore features

• Memcached

  • Multi-node for partitioning of data (sharding)
  • No high availability (replication)
  • Non persistent
  • No backup and restore
  • Multi-threaded architecture