For DataWatcher, swap out plain Integer key HashMap for a Int2ObjectOpenHashMap For ChunkProviderServer, swap out CB's custom LongHashMap with Long2ObjectOpenHashMap These collections are super fast as seen http://java-performance.info/hashmap-overview-jdk-fastutil-goldman-sachs-hppc-koloboke-trove-january-2015/
Importing the full library would double the jar size... its way too large. So lets just import the basic int/long based collections to then use to improve performance on these kind of collections.