Lightroom uses the SQLite database as it’s software for storing most of the information. Remember that Lightroom doesn’t change any photo, instead Lightroom stores all its steps in the SQLite database.

Depending on how you have set your catalog configuration, when you have set the backup of the catalog, Lightroom will optimize the catalog.

But you can optimize your catalog manually from the File menu. The question is when should optimize the catalog?

  1. After importing a “bunch” of photos. What’s a bunch? 50, 100 or more photos. Importing only a couple of photos, don’t bother.
  2. After deleting a “bunch” of photos. What’s a bunch? 50, 100 or more photos. Deleting only a couple of photos, don’t bother.
  3. After applying a whole “bunch” of metadata.
  4. After developing a whole “bunch” of photos.
  5. After creating manual collections and adding photos to the manual collections.

Don’t bother with Slideshow, Print, or Web.

I have set: Backup: Once a day, when exiting Lightroom. Then Lightroom will optimize the catalog after backing up.