Indeed. Appending to a table is not as cheap as appending to a file, because of B-tree relancing. But if your end result must be an SQLite DB, then unless you create it as a post-processing from some other append-only file(s), in which case those rebalances matter little, you have to accept the cost of appending to tables. Time-series databases certainly do exists, but are there any as small and beautiful as SQLite, with the same world-class quality as SQLite, and free too?