Comment by jmull

> The VFS interface is synchronous

On a single thread. There can be multiple threads.

Of course leaving a thread idle while waiting for IO isn't great. That's why I noted it at the beginning. But it doesn't seem idling threads has proven to be much of a problem with sqlite, so it wouldn't be much justification for a rewrite.

> If you want to wrap a blocking API in python, with actual parallelism, you have to use multiple processes

You can use multiple threads in the same process.

(Python has some limitations in that respect, but that's not a sqlite issue and can't be fixed by a sqlite rewrite.)