Similarly, the server-side has to rarely worry about the server killing a running process while it is normal for mobile OSes to kill backgrounded processes eventually. A network request running on mobile has to be robust enough to deal with intermittent broken connectivity to outright unavailability of a data connection, e.g., due to the user switching to the airplane mode. A network request on cellular would usually cost more than a network request on Wi-Fi to the user and a network request on roaming even more.