Every mob has multiple loot tables attached to his record. Zone Loot Table, Race Loot Table, Common Loot Table, and a mob-specific Loot Table. All of these Loot Tables are catenated together, then compared against a series of "rolls", which may be affected by droprate boosts currently in effect on you, specifically, or the server as a whole, to determine IF the mob you just killed drops anything and, if so, exactly what. All of this happens in the millisecond between when you drop him in the sand and the first player that opens the Loot Interface.
See DungeonLoots and Lootomatic for more information.