Configuring durability
When creating an ElastiCache cluster, you can set the --durability parameter to one of the
following values:
| --durability value | Behavior | EffectiveDurability (Valkey 9.0) |
|---|---|---|
sync |
Writes persisted to Multi-AZ transactional log before responding to client | sync |
async |
Writes persisted to Multi-AZ transactional log after responding to client | async |
disabled |
No durability; standard ElastiCache behavior | disabled |
default |
ElastiCache determines setting based on engine version and cluster configuration | disabled |
The EffectiveDurability property in the API response always shows the actual durability
mode in effect (sync, async, or disabled). Whether durability is enabled or disabled is determined at
cluster creation time and cannot be changed afterward. You can switch between sync and async modes on an
existing cluster by calling ModifyReplicationGroup with the --durability
parameter.
For snapshots, ElastiCache stores the EffectiveDurability value so that restoring from a
snapshot preserves the actual durability setting.
When you enable durability, ElastiCache automatically enables encryption at-rest on your cluster. All data
at rest is encrypted, including snapshots and data in the Multi-AZ transactional log. By default, the
cluster uses a service-managed KMS key, but you can also specify your own customer-managed KMS key. The
encryption status is visible in the StorageEncryptionType field for the replication
group.
