Read Models

Read models are documented in the shared Chronicle docs so the model stays consistent across clients.

• Read models
• Getting a single read model instance
• Projections
• Reducers

For JVM syntax, see the annotation reference and EventStore API reference.

Kotlin client: IReadModelsService

Beyond getInstanceByKey, the Kotlin client’s store.readModels exposes a richer surface for reading and managing read model instances:

Member	Use it for
getInstances	Every instance, replaying events in-process.
getSnapshotsById	Snapshots of a read model grouped by correlation id.
watch	A Flow of changesets for a read model — a live view.
dehydrateSession	Releasing session-scoped state for an instance.
release/releaseMany	Decrypts @Pii properties, one or many.
materialized	Paginated, server-materialized reads — see below.

To react to changes without collecting a Flow yourself, write a convention-dispatched reactor instead — see Read Model Reactors.

getSnapshotsById and watch both deserialize straight into the read model type you ask for — getSnapshotsById(EmployeeProfile::class, key) returns List<ReadModelSnapshot<EmployeeProfile>>, and watch(EmployeeProfile::class) returns Flow<ReadModelChangeset<EmployeeProfile>> — no manual JSON parsing either way.

val employees = store.readModels.getInstances(EmployeeProfile::class)
employees.forEach { employee ->
    println("${employee.firstName} ${employee.lastName}")
}

Materialized (server-side) reads

store.readModels.materialized provides paginated access to instances a sink has already materialized server-side, instead of replaying events in-process:

val page = store.readModels.materialized.getInstances(
    EmployeeProfile::class,
    skip = 0,
    take = 50
)

store.readModels.materialized
    .observeInstances(EmployeeProfile::class, skip = 0, take = 50)
    .collect { updatedPage -> /* re-render whenever the page changes */ }

getInstances returns a single page; observeInstances returns a Flow that emits a fresh page every time the underlying data changes.