Not trolling or trying to downplay anybody here, but honestly - how “kvass” (readed as “k-v-ass” given it is a “key-value” storage) is a good name?..
(Just in case you are unaware, kvas/kvass is a traditional north-eastern europe drink.)
I've never read it this way but now I can't unsee it.
You could call yeast kvas, but in slavic languages there are usually other nouns used. (drozdze, drozdie, kvasok, kvasnice, закваска , дрожжи). Kvas (the drink) is kvas everywhere.