How does the ranked rewards distribution work?

Hey I was wondering how does the ranked reward distribution work and why would it take that long? I am talking about the process behind it, does it go through all the players and checks if the player is eligible for the rewards? Wouldn't checking when someone logs in and processing it then makes it faster? Something like if one logs in ---checks if rewards received -------checks ranks and stuff ------------gives the rewards and rewards received gets checked otherwise continues with their life

Idk it's only going to send one query, idk I was just wondering why it takes that long. :3