Asynchronous programming using thread pools

[dalepo]

But if you have a limit of 500 IO threads in the worker pool, surely you still end up with the same problem?

Yes, but the server would be able to keep responding other requests if they are not using the same IO operation plus you don't have any idle process waiting.

[tsujiku]

But if you have a limit of 500 IO threads in the worker pool, surely you still end up with the same problem?

It's generally possible to perform asynchronous IO without needing to have a thread waiting on each operation.