Firstly, each ward is a "server program". To understand what a server program is... type in your windows search bar "cmd" and open the Command Prompt. That's what a server looks like.
Secondly, seeing as I have run game servers before, I can confidently say there isn't usually much overhead... to such a point, you can run multiple of them. In fact, SE does run multiple of them - they run 12 wards on a single physical machine, alongside several other zones and MSQ instances. We know this from their hardware failure reports where they reveal which zones were on that physical machine.
But you know what? Modern hardware is so good in 2025 that they could probably run a lot more server programs than they currently are on the same machine. Unless the server is hogging resources it shouldn't be (wouldn't surprise me, because it's SE), they could probably run hundreds of wards on one machine.
But anyway, SE has all these machines (yes, this is a picture of SE's machines and yes, each one of those cabinets contains hundreds of motherboards):
Based on the recent Ramuh hardware report, they had 36 server programs running on one machine. So to run 500,000 wards, they'd need 2 server programs each (ward server, and private room server), making for a total of 1,000,000 server programs. Thus, they'd need 27,777 physical machines. However:Again this is assuming 36 server programs is even their limit and did I forgot to mention that the server programs themselves could just be made to handle even more instances per program, taking advantage of modern hardware and multi-threading.
- The "30,000,000 adventurers" wouldn't all get a house. Many of them are bots or don't get beyond the first quests or are alts.
- Nobody is saying to have unlimited scaling wards. They are saying to have unlimited scaling instances.
- Instances are "freed" when not in use, allowing someone else to use them. This makes it scalable without needing to run 27,777 physical machines. Instead, you'd only need, say, 111 machine to account for up to 2 million active players spreading their activity through the week, leaving only 10% of them using their house at a time. And we don't even seem to have 2 million right now (more like half that) so we'd get away with 55 house instance machines.