Capacity Pool
A Capacity Pool is the dedicated Valkey capacity you provision. You declare its size and Momento provisions and operates the backing cluster, handling the instance lifecycle, reconciliation, and health. A Capacity Pool is the isolation boundary of Momento Cache.
Sizing a pool
When you create a Capacity Pool, choose one sizing mode:
- Cluster (explicit): specify instance type, shard count, replicas per shard, and availability zones.
- Flex (managed): specify capacity and replication bounds plus availability zones. Momento chooses and automatically resizes the backing topology within those bounds.
See Provisioning and sizing for how to choose these values and for the sizing modes the service supports.
Managing capacity
Pool capacity is the configured Valkey maxmemory on each primary shard multiplied by the number
of primary shards. Replicas do not add Pool capacity. Memory utilization is a separate measurement
of live used_memory relative to deployed maxmemory.
You can change a pool's size after creation by updating its configuration. Momento converges the running cluster to the new shape. Scaling behavior and safeguards are covered in Manage Capacity Pools.
The default account admission limit is 500 GiB of Pool capacity. See Service limits for the admission and usage distinction. See Capacity Pool metrics for memory, eviction, CPU, and network observations.
Lifecycle
A Capacity Pool moves through three states: creating, active, and deleting. You can
create Databases on a pool once it is active. Deleting a pool is rejected while any Database
is still assigned to it; remove the Databases first.
If Momento cannot provision the requested capacity (for example, when a cloud region lacks capacity for the requested instance type), the pool reports a diagnostic that you can read and monitor. The cluster does not have a failed state, since the control plane will continue attempting to converge to the target configuration.
To resolve a capacity diagnostic, update the pool's configuration (for example, choose a different instance type or zones). The control plane will adjust provisioning to match the new configuration. See the API reference for available diagnostic fields.
Databases exist within a Capacity Pool
A Capacity Pool provides the compute and storage for Databases. Databases in the same pool share its resources. A Database belongs to exactly one pool.