At one end of the market, arabica beans, known for their sweetness and aroma, are hand-picked at cool altitudes in Brazil, Ethiopia, and Kenya; it’s a careful process, even more intricate than the harvesting of grapes for the finest champagne. At the other end, robusta beans, known for their high levels of caffeine, are mass harvested by machines. Vietnam has cornered the market on robusta since emerging from its war in the 1970s.