public async Task <int> RunAction(
            [ActivityTrigger] IDurableActivityContext context)
        {
            WorkflowMessageEnvelope envelope =
                context.GetInputWithCustomSerializationSettings <WorkflowMessageEnvelope>(this.serializerSettingsProvider.Instance);

            ITenant tenant = await this.tenantProvider.GetTenantAsync(envelope.TenantId);

            IWorkflowInstanceStore instanceStore = await this.workflowInstanceStoreFactory.GetWorkflowInstanceStoreForTenantAsync(tenant);

            return(await instanceStore.GetMatchingWorkflowInstanceCountForSubjectsAsync(envelope.Trigger.GetSubjects()));
        }