Good points. I don't have a lot of experience with DuckDB in a production setting, but my team uses ClickHouse, where we ingest log and instrumentation data into materialized views at high volume. What I think saves the segmented/layered architecture there (ClickHouse calls them parts, but it's fundamentally the same thing) is that it's append-only, which means the "layers" don't go backwards, and a single row will never appear in more than one layer. But with a B+tree, the entire tree is mutable.