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For quite some time already and not to be used in production.

Yes, but AFAIK it is not multi-threaded so it's not fit for production, at all. It's good for development and testing.

And a built in debugger.

Yes. Since 6 years ago with release of 5.4 in 2012.

It's not multithreaded so it's impossible to use in production.

It's not meant for use in production. It's a lighter-weight substitute for a full Apache stack on development systems.