Instead of doing the obvious thing and build a database connected web application hosted in the cloud; I opted for a local application that generates static files for customer ordering, uploads them to a web server and polls for orders. On the server there's a simple PHP script that writes a chunk of JSON to a file when the order is created.
The main motivation was to allow them to continue taking orders in the restaurant and perform maintenance even if the internet connection isn't working. Generating files also simplifies the implementation of customer specific customizations.
And since the database isn't customer/web facing any more and therefore doesn't need to scale beyond a couple of simultaneous users, I opted for a simple file based solution.
The fact that the customer order part runs blazing fast is a nice bonus.