User blog comment:BadFish95/What is the Max Unit and Item Capacity?/@comment-24277289-20150227022152

Max unit capacity in Japan is currently 1000 and I believe it is the same for items. I believe that the Global cap is 500, but it may have expanded with the update. I haven't gotten even close to either of these caps myself, so I don't know for sure. Max key capacity is 15 for either type.