1. A computer-implemented method comprising: accessing a cumulative feature store storing feature values determined from user actions performed before a time point; accessing an incremental feature store storing feature values determined from user actions performed after the time point; calculating, by a computer processor of an online system, a weighted combination of feature values from the incremental feature store and corresponding feature values from the cumulative feature store; updating the cumulative feature store by replacing the corresponding feature values in the cumulative feature store with the weighted combination of feature values; receiving an update to one or more of the feature values stored in the incremental feature store, the update comprising a new value for one or more of the feature values; and updating the incremental feature store based on the received update by replacing the corresponding feature values in the incremental feature store with feature values in the received update.
1. A computer-implemented method comprising: accessing a cumulative feature store storing feature values determined from user actions performed before a time point; accessing an incremental feature store storing feature values determined from user actions performed after the time point; calculating, by a computer processor of an online system, a weighted combination of feature values from the incremental feature store and corresponding feature values from the cumulative feature store; updating the cumulative feature store by replacing the corresponding feature values in the cumulative feature store with the weighted combination of feature values; receiving an update to one or more of the feature values stored in the incremental feature store, the update comprising a new value for one or more of the feature values; and updating the incremental feature store based on the received update by replacing the corresponding feature values in the incremental feature store with feature values in the received update. 6. The computer-implemented method of claim 1 , further comprising: storing the incremental feature store in a data store that provides faster data access compared to a data store used for the cumulative feature store.