> With Python, in practice most systems end up based on Celery, with huge long-running tasks.

Oh dear... Yeah, that's a terrible distributed system. Interestingly, all the distributed systems I've worked on with Python haven't had Celery as any kind of core component. It's just poorly suited for the job, as it is more of a task queue. A task queue is really not a good spine for a distributed system.

There are a lot of python distributed systems built around in memory stores, like pycos or dask, or built around existing distributed systems like Akka, Casandra, even Redis.