(I’m not on the search team, but I did write some search stuff back in 2019, explanation may be outdated)
The blocks (pages are a block) in Notion are a big tree, with your workspace at the root. Some attributes of blocks affect the search index of their recursive children, like permissions: granting access to a page grants access to its recursive child blocks.
When you change permissions, we kick off an online recursive reindex job for that page and its recursive subpages. While the job is running, the index has stale entries with outdated permissions.
When you search, we query the index for pages matching your query that you have to. Because the index permissions can be stale, we also reload the result set from Postgres and apply our normal online server-side permission checks to filter out pages you lost access to but that have stale permissions in the index.
