as a last resort / as the last resort

Hello. I see both “as a last resort” and “as the last resort” used in various places.
Is my understanding correct?
as a last resort=one of the possible and final solutions
as the last resort=the final and only solution"
Thank you very much.

In my experience, the usual expression is “as a last resort”. If some people do say “as the last resort” then probably it is a more-or-less arbitrary variation. I don’t perceive that there are two separate expressions with two intentionally distinct meanings.