ExperimentalReadonly ExperimentalidReadonly ExperimentalkeyReadonly ExperimentalkindOptional Readonly ExperimentalrecordPresent for "create"/"update"; the accepted store's record (carries cursor/sequence/receivedAt).
Optional Readonly ExperimentalsourceOptional Readonly ExperimentaltombstonePresent for "delete"; the accepted store's tombstone, when the reducer still retains it.
One identity-stable change, keyed exactly like the accepted store (realtimeFeatureKey).