I downloaded a 50 megabyte world on my iPad, hoping I could use realms to transfer the worlds to my xbox one, as there is currently no other way to download custom worlds (besides Marketplace) on the Xbox one. However, it appears Minecraft has troubles with world files that are too big, as when I try to upload the world it takes much longer than usual, the progress bar sometimes says "0.0 out of 0.0 megabytes", sometimes the progress bar doesn't even load, and other times it will say it's uploaded to the realm, won't have the "Lets Go!" button, then as it turns out nothing happened because it has not been uploaded to the realm. In other words, Minecraft is extremely glitchy when it comes to uploading large save files to realms, a paid service that should work, even with worlds that are 50 megabytes or more.