I have read somewhere that you cannot use a key a second time on the same character ie. you use it, boom, golden chest disappears for that character forever.
Is this really true?
Sorry if this question is a bit too less informative.
This is specifically how it goes down:
You try and open the chest, and a prompt comes up asking if you're sure you want to expend a key (the key is gone forever). The key is consumed and the chest opens, holding a Red Chest's worth of loot, but everything is Purple or Magenta (not sure if Orange can spawn there, if it does it's crazy rare). You can open the chest again immediately for more loot only after you've removed all items from the opened chest (you can just pick them up and drop them or sell them).
The chest remains in Sanctuary and can be reopened any time with a golden key after the platform has been lowered.
The golden chest in Sanctuary is a persistent item and will not disappear even after multiple uses on the same character. The only thing you lose is a golden key every time you open the chest.