How many engineers work solely on scaling in your team?

I was seeing very product oriented companies struggle with scaling:

• to justify spending dev time on something you needed metrics
• metrics were easier to cook up for product work than for ease-of-development
• therefore engineers were trying to cope with systematic problems in stolen times between to product features

There is another angle here and that is work for scaling might not be as "linear" as work for a new feature, i.e. maybe 1 or 2 engineers can unlock the ability to serve 100 000 instead of 1000 users, while shipping 100x features would need more devs.

And the questions are...

• Do you have engineers in your team/company that only works for enabling the scaling to more users?
• If so, what is the ratio to product devs?
• And is it enough? I.e. there is no anxiety about the infrastructure collapsing if you add significantly more users (or devs... think of build automation, internal tools, etc.), or having the ability to do proactive work instead of reactive?