How exactly does duping work?

I asked Nano if duping would be patched in his ROTMG server, he said this:
duping was only due to the server side and the way google data store works. It costs money per transaction, and they decided to batch transactions together so they kind of made a bad mistake. My server is independant of all that kind of stuff, so it's not effected by it

It sounds like its a way that Kabam tried to save money, but instead it allowed duping? Maybe?

That's what it sounds like to me. Thanks for sharing. It is nice to know a little be more on why it was possible.

Okay, so a client will sometimes block SOME things guarded by wildshadow. Some things wildshadow patches to keep OUT duping, it removes, but not enough to make it obvious that somebody has been tampering with the server. The duping client is basically a proxy to the REAL game, a modified version, that most of the time allows you to duplicate items.

I'll explain how duping work

1. The client take items from vault : in 123.5 and lower, the server was registering the inv ONLY when you change realm/server. But now, it register each time you change an item from your inv (this is why its a bit laggy)
2. He nexus, but before he have the time to register you dont have them in your inv, the other client connect with the items in the inv!

I hope it helped a bit

Sorry i'm not english :/