Not sure if this should be a "Realms" issue or "PocketEdition/Win10" issue.

Longer version of issue in the Minecraft Forums. Here is the shorter compact version:

TLDR - Realms larger than certain point become too laggy/unresponsive to play on PE Realms.
Here is the slightly longer version:

This is now the second time our Realm world has gotten larger than 1GB (previously was 1.98GB at the end of season 1), and has gotten to the point of instability not allowing play often for more than 10-20 minute without it crashing. We will be reseting again after only 5-6months, to start season 3 due to this once 1.1 comes out.

There are time where the realm will be stable for hours, and then just stop working. From our testing it doesn't seem to be specific chunks that are effected, certain players, or items. There doesn't even seem to be certain times of the day that are better than others. Players will be unable to log in, get disconnected (as a group), have chunks that won't load, blocks that won't update... The issue just seems to get worse and worse as time goes on. Usually when small updates happen (1.0.3, .4, .5, etc) it gets better for a short time, but then returns after a few hours to a day.

I've downloaded this world and although slow on my local computer I've never had crashes, or ejections in any of the areas. Different tools I've run on the downloaded don't seem to come up with anything either that should be causing issue. Only thing I can think of is Realms can't handle world sizes over a certain limit, although have never found any official documentation supporting this. Anecdotally, I have been able to confirm that once the realm gets to roughly 1GB it can no longer be uploaded, as we used to try to check if there were issues or cheating going on by uploading the backup to a second realm.

I can upload the backup here if that would be helpful, or provide a link to our gDrive that has the file. Also I can give the realm's Creator info or transaction number if it's better to se the world live in action. Any information would be appreciated as seems we have to reboot the word every 5-6 months.