How to change state, when 1 mutation worked, and you need to fetch result with another mutation?

Ecom project. On pages with catalog list, i have product cards, when i press on "add to cart", i send request to server. After that, i want on cart icon in header counter to appear, showing the number of cart.products.length. My backend partner says, he can send cart items in response to api/add_to_cart. That is ok, But is there any way to listen to add_to_cart and update state instantly in header? i try to do this, but sometimes await refetch() works before data is on the server