Sourcing::Plugin::StateCache

Abstract role defining the interface for state caching backends. State caches handle the storage and retrieval of projection state for faster recovery and reduced event replay overhead.

Overview

The StateCache role handles projection state persistence:

State storage — caching projection state to avoid full replay
State retrieval — fetching cached state for fast recovery
Version tracking — tracking the last processed event ID

See also: Sourcing::Plugin::EventStore for the event storage interface.

Abstract Methods

method store-cached-data(Mu:U, %)

Stores the current state and version of a projection. Implementations should persist the projection data along with the last processed event ID.

Parameter	Type	Description
`Mu:U`	Type	The projection type
`%`	Hash	Additional data to cache (IDs, state, etc.)

method get-cached-data(Mu:U, %) is rw

Retrieves the cached state and version for a projection. Returns a Hash with last-id and data keys.

Parameter	Type	Description
`Mu:U`	Type	The projection type
`%`	Hash	Identity criteria

Returns: A Hash with:

last-id — The last processed event version (atomicint, defaults to -1)
data — The cached projection state (Hash)

Class Methods

method use(|c)

Activates this plugin as the current sourcing configuration by setting PROCESS::<$SourcingConfig>.

Sourcing::Plugin::StateCache::Memory.use;

Use Cases

State caching is particularly useful for:

Fast recovery — Load cached state instead of replaying all events
Read performance — Serve cached projections for high-read scenarios
Hybrid approaches — Use different backends for events vs. state