Short version: That warning just means “you tagged this task with qc, but there isn’t a concurrency limit configured for that tag, so Prefect isn’t throttling anything.” Details and how to fix (if you want throttling): - Tags alone don’t enforce limits. You must create a concurrency limit for that tag. - Prefect internally displays keys like

tag:qc

in logs, but when you create the limit you should use just the tag name

qc

(no

tag:

prefix). CLI (Prefect 3.x): - Create a limit of, say, 1 for the qc tag:

prefect concurrency-limit create qc 1

- Inspect/list:

prefect concurrency-limit inspect qc
  prefect concurrency-limit ls

- Delete when no longer needed:

prefect concurrency-limit delete qc

Docs: - Tag-based concurrency limits - CLI reference: concurrency-limit Tagging a task (examples):

from prefect import flow, task

@task(tags={"qc"})
def qc_task():
    ...

# or ad-hoc for a single call
qc_task.with_options(tags={"qc"})(...)

If you only added the tag for metadata and don’t want throttling, you can ignore the warning. If you did want throttling, create the limit with the command above. Want me to suggest a limit value based on your workload?