Using FULLTEXT indexing will in increase the speed of posts searching by its title.
Do next:
- open your site database using phpmyadmin page
- enter to your site database
- find table "wp_posts"
- click on tab "Structure"
- find field "post_title"
- find on the right side and click "More" -> "Fulltext"
- on the popup click OK and wait a little
Also read related to this theme:
- https://makandracards.com/makandra/12813-performance-analysis-of-mysql-s-fulltext-indexes-and-like-queries-for-full-text-search
- https://www.mysqltutorial.org/activating-full-text-searching.aspx/
- https://www.digitalocean.com/community/tutorials/how-to-improve-database-searches-with-full-text-search-in-mysql-5-6-on-ubuntu-16-04
