The name is a bit misleading. Your patron is actually the Spirit of Cheese. You also have to choose the Pact of the Rules Lawyer.What the heck is a coffeelock, does the character make pact for magical power with a Starbucks Barrista, or the spirit of Canadian Coffee Titian Tim Horton?
Basically, some joker observed that sorcerer spell slots created using Font of Magic last until your next long rest. And there is not, by the book, any limit to how many you can create. So, if you make a multiclass sorcerer/warlock, you can use your sorcery points to create sorcerer spell slots; take a short rest; burn your warlock spell slots to create more sorcery points; and repeat ad infinitum. As long as you never take a long rest (thus, "coffeelock"), you can accumulate unlimited slots this way.
It's an absurd build, and the idea that the designers should waste their time addressing such extreme rules-lawyering is silly. A DM who doesn't shoot this one down deserves whatever they get. There are certainly balance issues in 5E that ought to be dealt with. This is not one of them.