Restaurant sign contract with Grab.
Grab get like 18% (i forgot) share from restaurants' sales.

When customer place order, system will notify restaurant to prepare the food.
After restaurant confirm order, system will assign the task to nearest available courier.
Courier receive notification where to pick up the food and where is the delivery address.
If he arrive early he will have to wait for the restaurant to prepare the food.
If there is no available courier like for an hour (i forgot the exact time limit) the order will be unfulfilled. Customer get their money back and restaurant get their bill covered by grab and the food get wasted.