Reliability

A high-availability (HA) configuration should have at least one replica per shard and span at least two availability zones. A high-availability configuration can still result in data loss due to catastrophic events, such as a full region outage at the cloud service provider.

Replication

Each shard in a Capacity Pool can have zero, one, or more replica nodes in addition to the active primary node. At least one healthy replica per shard makes the Pool capable of failing over when a primary node becomes unavailable.

Multi-AZ placement

You configure which availability zones a Capacity Pool can use, while Momento distributes Valkey nodes across those zones. At least two zones, together with at least one replica per shard, make the Pool capable of tolerating a single-zone failure.

Managed operation

The Momento Cache control plane manages the underlying cluster based on your specified configuration. It automatically provisions and replaces nodes, including promotion of a healthy replica when a primary is lost (failover). Momento also applies CVE patches and version upgrades through managed rolling operations.

Automatic Rolling Updates

Changing some configurations like instance type triggers a rolling update. The service works one shard at a time, adding a healthy replacement before removing an old node. This approach minimizes disruption during the change.