I am using PHP and MySQL to handle data for my multiplayer iOS game (building for Android to) and the game is tarting to be a success. I have at high traffic times about 3 calls pr. second to my "move.php" page. It takes the players move and saves the data in my db and after that returns a "completed". I need this to make sure nothing went wrong. When there is high pressure it takes about 3-5 seconds before I get "completed" back and some times more. I'm hoping to get 10 times as many users as now and are in fear of this making either the response time very long or it starts to fail... In my move.php page i have about 5 different select queries, 4 update queries and 2 insert queries. This part is optimized, but I use regular mysql and php. 

I am wandering what is good practice at this point and how do I make this faster, specially for the "completed" to be sent back. I don't mind the long executing time afterwards as long the user don't experince this. Does mysqli, pro, stored procedurs etc. do anything for me?

Hoping for answers and thanks in advance...