Old School RuneScape is so old and so big that the devs are about "to run out of" a key tech resource and have to do "a bunch of work to stop the game exploding soon"

Anti-clickbait: the game stores object IDs in, presumably, a 16-bit integer. In 2018 they changed it from signed to unsigned, but now they’re about to hit 65535 and will have to do something about it.

The games journo is, of course, too clueless to actually figure this out or talk about it in the proper terms:

I’m blindly assuming, just going off standard number patterns in code and OSRS history, that 64000 is the brick wall here.