Durable State and Event Sourcing for Actors

public class SubscriptionActor : ReceivePersistentActor
{
    private SubscriptionState _state = SubscriptionState.Empty;
    public override string PersistenceId { get; }

    public SubscriptionActor(string subscriptionId)
    {
        PersistenceId = $"subscription-{subscriptionId}";

        // Handle commands — process, persist, react
        Command<UpgradeSubscription>(cmd =>
        {
            var events = _state.ProcessUpgrade(cmd);
            PersistAll(events,
                evt => _state = _state.Apply(evt),
                onComplete: async () =>
                {
                    await SyncReadModel();     // sync EF Core projection
                    await SendConfirmation();  // email, notifications
                    Sender.Tell(new UpgradeComplete());
                });
        });

        // Recover state on startup — replay events from journal
        Recover<ISubscriptionEvent>(evt =>
            _state = _state.Apply(evt));

        Recover<SnapshotOffer>(snap =>
            _state = (SubscriptionState)snap.Snapshot);
    }
}