When you write an article on WordPress, system apply a auto save cron job. Auto saving useful, but sometimes autosaving make a lot of problem. First problem is database. This saving job create a lot of mysql queries and your datebase have a big size. And second problem is post revisions. Sometimes post revisions have error for our editing. You can look how to delete revisions article.

You can disable auto save with this code. You can edit/create your functions.php. Be careful and make back-up.

function disableAutoSave(){
 wp_deregister_script('autosave');
}
add_action( 'wp_print_scripts', 'disableAutoSave' );

Have a nice day!