Barely any servers?

[cezarica]

The server that was down due to whatever reason was actually hosting a database with the public available servers, so when you make your own player hosted or dedicated server, be it windows or linux, basically you are telling the Master what information the clients would need to connect to it, world info, active players, mods and so on.

As a client when you want to play you ask for the list of active servers and the Master feeds you the list (most likely JSON format) and on client side you can filter what you wish to see in the list.

You don't need too much power for this, the problem is the amount of incoming and outgoing connections and the upload speed it can deliver the above mentioned list.