There’s suboptimal query in admin/orders.php page which retrieves information about last orders. Unfortunately query is constructed in such way that MySQL scans whole orders, orders_products and orders_total table. As always it’s not a problem until orders table gets big ( for example 50 000 entries ). If You happen to have at least 10 000 orders ( I wish You that 
), You probably get impatient each time You request admin/orders.php page.
Good news is that there is quick fix. Just add index on (orders_id, class) on orders_total table to speed up the query. Here’s MySQL statement which does that for You:
The query is still suboptimal, but at least its quite fast until orders table gets really big (500 000 orders? It’ll depend on Your server).
