In my country we have 220V and most electric meters allow up to 30A, you can ask for an upgrade for 40A.

My question is the following: when electricists design the connection from an apartment building of say 100 units with their own 30A meter to the grid. How do they do it? They set it up considering an average consumption? Or the give enough capacity to the connection for the 100 units to be running at 30A?

I assume we all share a thick cable than then goes thinner to each meter?

Sorry if asked something stupid. I am a bit ignorant on this topic.