@lukolas The example you provide sees to be REGEX not expression language. You would need to test some kind of expression language in that Topic Name(s) property.
Another suggestion would be to have a file, or for example generateflowfile, which contains a list of topics. Then split/extract that list into attributes, then send that attribute to the topic name.
Having a ton of topics going to single processors can become a bottleneck which creates tons of downstream flowfiles from each topic. So be careful with tuning and concurrency in reference to number and topics and messages per topic.
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