[Answered ]-How to rate limit Celery tasks by task name?

An alternate solution is to queue my_really_long_task into a seperate queue.

 my_really_long_task.apply_async(*args, queue='foo')

Then start a worker with a concurrency of 1 to consume these tasks so that only 1 task gets executed at a time.

celery -A foo worker -l info -Q foo