How does nginx handle long running requests like file downloads?

From my limited understanding of nginx I know that nginx seperates itself from Apache by using a single thread that handles all requests instead of Apache which throws threads at the problem. In theory with a bunch of small requests its faster. But what about long running requests.

Lets say a user is downloading a large file or there's some long running PHP script that's slow because of something its depending on (disk IO, database) is slow. With Apache everything has its own开发者_JAVA技巧 thread so while PHP is waiting for a response from the database another request can come in and be simultaneously processed. With nginx however, wouldn't something like that lock the thread and therefor the whole server? I know that you can have multiple nginx processes but creating more processes for just file downloads just seems like trying to recreate Apache.

I know I'm missing something here as nginx handles situations like this, but what? How does nginx do this with its threading model?

And before you say it, this isn't a duplicate of this question as it only talks about incoming connections

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Worker processes in nginx can handle multiple incoming and outgoing requests simultaneously. The answer to the question you linked (3436808) is also applicable to this question.