Youtube would be a prime example: I'm guessing the storage required for the metadata of all videos is too large to be stored on a single server, so how do they achieve millisecond-level performance on searches and handle millions of queries routinely?

What kind of infrastructure and technology is required for this?

Do you have any resources I could use to learn more on this subject?

To my understanding:

Many terminals are capable of displaying multiple fonts at the same time, say latin unicode characters in font foo and japanese unicode characters in font baz. In urxvt at least, it is also possible to have one font in a certain size and the next font in another size. However, no font can have a size bigger than the base size, the size of a terminal cell.

Why is it not possible to have multiple terminal cell sizes? For exampleso one line has terminal size 8 and the next line has terminal size 12.