We just implemented a LRU (least recently used) cache . That means, downloaded and encrypted files from the cloud will be stored locally on the device. The next time this file is accessed, it is just loaded from the file system (if there is no newer version of this file in the cloud).
This feature decreases significantly the access time to the files and introduces a massive network bandwidth reduction. We will release this in one of the next versions of Cryptomator for Android.