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AWS Solutions Architect Associate (SAA-C02)


  • Regional Service
  • AWS managed caching service
  • In-memory key-value store with sub-millisecond latency
  • Need to provision an underlying EC2 instance
  • Makes the application stateless because it doesn’t have to cache locally
  • Using ElastiCache requires heavy application code changes (setup the application to query the cache before and after querying the database)
  • Usage:
    • DB Cache (lazy loading): cache read operations on a database (reduced latency)
    • Session Store: store user's session data like cart info (allows the application to remain stateless)
    • Global Data Store: store intermediate computation results

Redis vs Memcached

Redis Memcached
In-memory data store Distributed memory object cache
Read Replicas (for scaling reads & HA) No replication
Backup & restore No backup & restore
Single-threaded Multi-threaded
HIPAA compliant Not HIPAA compliant
Data is stored in an in-memory DB which is replicated Data is partitioned across multiple nodes (sharding)
Redis Sorted Sets are used in realtime Gaming Leaderboards
Good for auto-completion
Multi-AZ support with automatic failover (disaster recovery)

Security & Access Management

  • Network security is managed using Security Groups (only allow EC2 security group for incoming requests)
  • At rest encryption using KMS
  • In-flight encryption using SSL
  • Use Redis Auth to authenticate to ElastiCache for Redis
  • Memcached supports SASL-based authentication

Last updated: 2022-05-20