AWS Service - ElastiCache

ElastiCache:

• Overview

  • The same way RDS is to get managed Relational Databases

  • ElastiCache is to get managed 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 maintenance / patching, optimizations, setup, configuration, monitoring, failure recovery and backups

  • Note: Using ElastiCache involves heavy application code changes

• Solution Architecture - DB Cache

  • Applications 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

• 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

  • Multi AZ with Auto-Failover

  • Read Replicas to scale reads and have high availability

  • Data Durability using AOF persistence

  • Backup and restore features

  • Supports Sets and Sorted Sets

• ElastiCache - Memcached

  • Multi-node for partitioning of data (sharding)

  • No high availability (replication)

  • Non persistent

  • No backup and restore

  • Multi-threaded architecture

• Cache Security

  • ElastiCache supports IAM Authentication for Redis

  • IAM policies on ElastiCache are only used for AWS API-level security

  • Redis AUTH

    • You can set a “password/token” when you create a Redis cluster

    • This is an extra level of security for your cache (on top of security groups)

    • Support SSL in flight encryption

  • Memcached

    • Supports SASL-based authentication

• Patterns for ElastiCache

  • Lazy Loading: all the read data is cached, data can become stale in cache

  • Write Through: Adds or update data in the cache when written to a DB (no stale data)

  • Session Store: store temporary session data in a cache (using TTL features)

• Redis Use Case

  • Gaming Leaderboards are computationally complex

  • Redis Sorted sets guarantee both uniqueness and element ordering

  • Each time a new element added, it’s ranked in real time, then added in correct order

Relevant Doc:

https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/WhatIs.html

https://docs.aws.amazon.com/AmazonElastiCache/latest/mem-ug/WhatIs.html

Disclaimer: This is a personal blog that might come in handy when I suffer from Dementia in future.