#5: Optimize the Lightroom Catalog and Connection Speeds
The Lightroom catalog can be “optimized” if things seem to be running a little slow. To optimize the Catalog, go to File > Optimize Catalog, which in theory should make everything run faster. Selecting this option will close Lightroom so the catalog can be worked on, and then it will reopen it when it is finished.
If you have your images or the Lightroom catalog on an external hard drive (USB or Firewire), this can massively slow down everything in Lightroom as it is limited by the connection speed of the hard drive. I would suggest putting the main Lightroom catalog on a faster drive with a SATA or Thunderbolt connection if possible, or better yet, leave it on the computer’s main internal drive. This is one of the major factors in how fast Lightroom performs.