After some experimenting with saving/restoring of cache queue, the final design is to have cache queue constantly living in database. There is a "Clear queue" menu option to clean it up. It makes cache controllable. The only concern now is that populating of the queue on "Cache area" is quite slow. It's writing to the database instead of memory. Personally I could leave with it, should probably disable "Cache area" menu entry for the time when recursive algorithm is still working.
Will try to release new version tonight. There is annoying accuracy circle I need to recalculate so it scales closer to reality.