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If you face the problem, that Fetcher fetcher helper usage is permanently above 96% and Fetcher fetcher count is already high (i.e. >50 or 100 or more) then this is a strong indicator that you might have plugins/local checks (primarily in Windows) that have a quite a long runtime.
Increasing the fetcher helper further here is not constructive. Instead you have to identify the long running plugins/local checks and set them to async async and define a (generous) cache settings or even timeouts especially for them.
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