Annoyingly, this article does not say what alleles of rs762551 increase the metabolization of caffeine, so I had to look it up. C/A and C/C are the slower variants; there's apparently little difference between C/A and C/C metabolization according to SNPedia. A/A is ultrarapid metabolization. The article implies only A/A is good to go.

Useful if you had a DNA test and want to look up what you are--which I have and did immediately after reading this. Thankfully, I was A/A.

Sauce: https://www.snpedia.com/index.php/Rs762551