ErrorDocument 404 /404.html

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteBase /

    RewriteRule ^api/(.*)$ backend/_core/index.php [QSA,L]

    RewriteCond %{REQUEST_FILENAME} -f [OR]
    RewriteCond %{REQUEST_FILENAME} -d
    RewriteRule ^ - [L]

</IfModule>