Question: Is ElastiCache durable?


Amazon ElastiCache provides two types of durability for data storage - in-memory durability and persistence to disk. The choice of durability option depends on the use case and requirements of the application.

By default, ElastiCache stores data in memory for faster read and write operations. However, data stored only in memory is volatile and can be lost if there is a node failure or maintenance activity. To overcome this issue, ElastiCache provides a feature called "Automatic Failover" that automatically promotes a replica node to primary if the primary node fails. This ensures that the data is still available even after a node failure.

To enable persistence to disk, ElastiCache supports two engines - Redis and Memcached. Both engines provide different mechanisms to persist data to disk.

Redis provides two persistence options - RDB (Redis Database Backup) and AOF (Append-Only File). RDB periodically saves a snapshot of the dataset to disk, while AOF logs every write operation and replays it in case of a restart. ElastiCache also allows configuring replication groups with Multi-AZ and read replicas, providing additional redundancy and failover options.

Memcached provides an option called "Cache Persistence with Replication" that stores data in memory and disk simultaneously. When a node fails, data can be recovered from the disk copies.

In summary, ElastiCache provides options for both in-memory durability and persistence to disk, ensuring data availability and durability based on the requirements of the application.

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