Why my caching is slower that regular sql query? (file driver)

Depends on the system. If your database is faster than your filesystem the database can handle something like that faster.

But if you look at your numbers your content download takes WAAAAY longer and is most of the time difference. Are you sure you're sending the same result and the cached result isn't a LOT bigger?

return \Cache::remember('threads', 120, function () {
    return ThreadResource::collection(
        Thread::with('tags')->getThreadsByScope()
    );
});

@ftiersch I think you right, I have look at the file which laravel cached it have 395977 character hence that the page load the that huge number and become so slow!