You are right, I realize I misjudged/simplified the problem somewhat. My mind had spontaneously formed this idea of an in-memory overlay b-tree of committed (W

You are right, I realize I misjudged/simplified the problem somewhat. My mind had spontaneously formed this idea of an in-memory overlay b-tree of committed (WAL) but not yet merged changes... But thinking it through further I have to admit that this would quickly lead to a complexity explosion (MVCC'ish). I also notice my tone in that comment was more snarky than I meant to be, sorry for that. However I still believe that this is a wheel that's been reinvented often enough (and that is complex enough) that it'd be a good idea to focus on researching how the others have eventually solved it - to minimize the risk of repeating history.