Note: I don't play D&D, but reading some of the Hot Network Questions about saving throws (particularly Does Evasion allow half damage even when unconscious?) has made me curious.
According to the rules on death saving throws, taking damage means failing a death saving throw. Suppose I cast Magic Missile using a 1st level Spell Slot at a creature or PC with 0 HP, but which hasn't failed any death saving throws yet. Since all 3 darts hit, does this mean the creature or PC fails 3 death saving throws? My interpretation of the rules leads me to believe yes, but I'm not fully sure.