Mine has an electronic combination lock but also has a key. If I lose the key and the battery goes dead, I can send the SN of the safe to the manufature and get a key for it.
Or replace the battery?
I have a combination lock with key also, but I have two physical keys that I store away from the safe. If the lock fails at a critical time, I have a fighting knife on top of the safe or a second safe with my (silenced) 1911, and I'll have to settle for one of those.