Hi @Ingo_Richtsmeier ,
Thanks again 
Regarding the external task pattern. See: https://forum.camunda.io/t/best-practices-for-updating-central-state-from-external-task-workers/31286
Though correlated in my use case, it seemed like a different topic to me. That’s why I posted it in a separate item.
For the second part. I know that it could also be done with the regular retry cycle, but I hoped to visualize the retries. So that when we could use optimize, we can visualize the impact of the QoS of the REST service. And that may help in getting this REST service scaled to a higher throughput.
I did not realize that the current setup causes more database interaction. So in that sense it may also be helpful to use that approach.
What would be really great, is if I could configure the maximum number of concurrent executions of an activity in the cluster. To my knowledge that is not possible. I also studied the code like the “selectNextJobsToExecute” query to see if I could propose some extension there, but it seems hard at first sight because I could not find a notion of a configuration per activity in the schema.
Doing this at process level would be easier to accomplish, but then it would throttle the whole process and the purpose is to throttle an activity to match the QoS of an external service that is invoked from the activity.
Do you know if this is currently supported (and I just missed it) or something that is being worked on for a subsequent release?
Patrick