[jvanderbot]

All correct. An additional comment is that, when I was coming up, parallelism in its many forms was of the variety "I need to do this job in parallel" or "I need to handle exactly 32 concurrent workers". After web & such, it was common to just think of paralellism as "I declare this one method as returning a promise" and then "async def", which semantically is very different than managing threads. As pointed out, it's now more like "This function is basically a server for any and all uncontrolled calls from elsewhere".