[BetterRed]

I only put content descriptors in the Tags/tags column, I have a couple of columns with a fixed set of values for administrative usage.

BTW - Kovid and chaley made changes to calibre's in-memory database that made startup times significantly faster, but that was years ago - maybe as many as 4 or 5, or more.

I have a library of 180K books with 5 custom columns, another with 10K books and 12 column columns, and a Test library with ~2K books and 20+ custom columns. Calibre start up times are about 5 seconds no matter which library I start with. And that includes whatever Job Spy and Calibre Spy do at start up. Custom columns that access the file system via templates can make start up times slow, but i don't have any of those.

Added: the libraries are on a spinning SATA 3 HDD, calibre and settings are on an M.2 NVMe SSD. FWIW I have calibre portable installed on the HDD, startup times against the same libraries are not significantly slower, maybe 7 or 8 seconds rather than 4 or 5.

BR