As of TYPO3 v8.7.25, v9.5.6 and v10.0 this extension is no longer required, as the behaviour of this extension has been merged into TYPO3.
This extension disables the "Page is being generated" message which is shown when two requests try to render the same page simultaneously.
Disabling that message means that all concurrent requests render the same content independently.
TYPO3 implements the "Page is being generated" message through a "temporary page cache" concept. Instead of using a XCLASS, this extension hooks into the TYPO3 Caching Framework. We simply invalidate the timeout of the aformentioned temporary cache, so that the temporary content is never valid and thus never sent to the user. This does not affect delivery of cached page contents. They will be sent as usual as they are not marked as temporary cache content.
No configuration needed. Just install:
composer require qbus/skip-page-is-being-generated