How Do Google Algorithmic Slow Rollout Work?
Google often says that is algorithmic updates, be it core updates, page experience updates, and other search related updates can take several days to several weeks or even several months to fully roll out. I was asked on Twitter by an SEO named Jabroni Slayer "How exactly (technical explanation) do they roll it out several weeks?" It is an excellent question and I will share how I think this works, keep in mind, I did not confirm this with Google, but I think I know how it works - Google can always correct me if I am wrong. Now, I think there are multiple parts to this answer. Let's start with the core updates or quality updates. When Google pushes those out, it takes approximately two weeks to fully roll out because Google has to assign the new quality signals to each URL in its index. URLs that are indexed and recrawled and reprocessed often, like sites that get crawled a lot because Google knows they are updated often or the pages deem a lot of crawl budget, then those URLs often see the new scores assigned to them sooner. But URLs crawled less often, may take more time for Google to reprocess those URLs and assign the scores to them. So it can take Google two weeks or so to adjust the rankings and assign new scores to those URLs, depending on how fast Google reprocesses the index of URLs. Also, sometimes, those scores might be based on reprocessing other scores. So it can take time but I think it is mostly about how Google assigns various scores to URLs when it reprocesses those URLs. That is my simplistic understanding of how it works with core updates and the like. But with changes like the page experience update, yes, there is the reprocessing URLs aspect and that can take time. But not like two months of time... In this case, Google is pushing out different aspects of this update over the next two months. Like, signed exchanges went live a month ago, today the top stories eligibility change went live, the AMP logos are going away now also, and then of course, the scores for each URL takes time to be processed. Maybe more time because there is this 28 day core web vitals lag from the CrUX data to when it gets updated. So some updates, Google releases aspects of the update in different batches but also, there is the reprocessing each URL to be assigned its new score. This was some what how Panda and Penguin use to work, but now it is processed more in a real time fashion. I assume at some point, core updates and other updates will become more real time where scores can be updated much more rapidly without any specific algorithmic update push. We even saw Google confirm that Panda updates were pushed manually at various intervals as well. Here are some of those tweets:  Note, Google can also tweak these algorithms during the rollout if they see things they can do better or adjust as it is rolling out. Although, Google said in the past, it does not do this, but it can:  Panda 4.2 specifically may have had some technical issues for its rollout, so it was a weird one. But webmasters have noticed rollouts go at a crawl rate pace which makes sense. Finally, there is always the aspect of that Google has tons of servers and data centers. And while nowadays, Google is very quick to have them all in sync, there is a delay between data centers and those data centers getting the most recent updates. Again, this is my best guess on how slow algorithmic updates technically work. It is a simplistic overview. Forum discussion at Twitter.