This morning, we had a small release that we believe will make a big impact on the quality and consistancy of Search. We have moved from a crawl system to a feed system. In our previous crawl mode, the GSAs handled discovery and indexing inworld data with its own schedule and rules. With the new feed system, we generate and push content to the GSAs for indexing and have more control over when it is updated.
Please see our release notes!
Expect that ranking will be changing, and will settle by end of day. We have also published an update to the Search FAQ.