You get exp based on time to finish a map, the more time it take, the more exp you get which is kind of a backward way of thinking since getting no medal is better than a diamond medal but whatever.

The time is capped at 10 min though so you wont get more exp if you finish after 10 min.

You get 30k exp for finishing after 10 min, or 60K if you are on a server (you can host one yourself)