In Postgres this effect is huge since there aren't primary indexes. All tuples for a table get mixed up together in the heap, so a large table will tend to havi

In Postgres this effect is huge since there aren't primary indexes. All tuples for a table get mixed up together in the heap, so a large table will tend to having only 1 hot tuple per page. Additionally, every update and delete leaves a dead tuple to implement MVCC, and these are much easier to clean up with VACUUM on a small table. I'm not as familiar with sqlite, but it might have a similar problem in this case since the primary clustered index is on rowid and not a value that correlates with whether the queue item is running.