For others who were left scratching their heads at what exactly this pop-sci-explained PoolCounter mechanism actually is:<p><a href="https:&#x2F;&#x2F;wikitech.wikimedia.org&#x2F;wiki&#x2F;PoolCounter" rel="nofollow">https:&#x2F;&#x2F;wikitech.wikimedia.org&#x2F;wiki&#x2F;PoolCounter</a><p>TL;DR:<p>It&#x27;s a limiter on how many workers start rendering the new page version when the old page version in cache has been invalidated.