The sliding-window runtime for scalar indexes — shared by the server and the embedded store (one implementation, so the two faces cannot drift): boundary maintenance, the eviction slide, and the cold half of range/count.
Cold segments are derived spill, not truth (the rows stay hot; the index is rebuilt from them on boot) — so a failed slide simply leaves the tree untouched (the batch is read before it is cut), and a restart drops the segment set and re-slides. Every public item here is documented and the lint holds it.