If you are in a food delivery business, it doesn't make sense to me to ask for a review just after the order is marked as completed by the delivery guy.
(Why would I give a rating when I have not even open the parcel and tested the food?)
The best way would be to trigger this via push notification after like 30-40-60 minutes after the order is completed. (So that by that time the customer have enjoyed the food)
Another good way is to show a block on top of the footer on the homepage after 30-40-60 minutes and ask for the review.
And the best way I have seen is just ask for the review for the delivery when the order is completed, and for the product review wait for the customer to consume the food.
Guys please discuss the possibilities and suggestions and best way of implementation rather than just posting +1 +1 +1