When we talk about the performance of Drupal, the first thing come to my mind is caching. But today I found another way to make Drupal run a little bit faster. It is not a profound thing, but something may be ignored by many. In work, I need process 56916 records constantly with automated Cron process. It took 13 minutes 30 seconds to process all those records. Adding a new database field index, I reduced the processing time to one minute 33 seconds only. It is more than eight times faster.