Elasti Cache
Indroduction​
- 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 |
| 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