Why I don't feel like caffeine affects me? Why I'm never hangover?

Although I've been drunk a lot of times (VERY drunk), always the next morning I feel like brand new and I don't feel like caffeine affects me either, I can take two cups of coffee and go to sleep normally, or I can take redbulls and I won't feel energized.
I don't know anybody else with the same thing, is it normal?
Why I don't feel like caffeine affects me? Why I'm never hangover?
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