Skip WordPress handling 404 on static files to avoid lack of performance.

speed-up-404-static-files.php

<?php
/**
 * Plugin Name: Speed Up 404 Static File
 * Description: Skip WordPress handling 404 on static files to avoid lack of performance.
 * Author: GeekPress
 * Licence: GPLv2 or later
 * */

$path = parse_url( $_SERVER['REQUEST_URI'], PHP_URL_PATH );
$path = explode( '/', $path );
$abspath = explode( '/', ABSPATH );
$path = implode('/', array_diff( $path, $abspath ));

$extension  = pathinfo( $_SERVER['REQUEST_URI'], PATHINFO_EXTENSION );
$extensions = [
	'php'   => 1,
	'html'  => 1,
	'json'  => 1,
  'xml'   => 1,
];

if ( strlen( $extension ) > 0 && ! isset( $extensions[$extension] ) && ! file_exists( ABSPATH . $path ) ) {
	status_header( 404 );
	die();
}