If we rephrase question to the material reality of "What will we do when we're pulling in $20,000,000 a month?" then you can see how silly it is.
I dunno, just buy a company then and use their stuff? It's literally not a problem that a pre/early-revenue company should or realistically can solve. It's part of "founders delusion" - the same kind that make them get a huge office that's mostly empty or all that unused computer hardware sitting in the closet. It's just gambling.
It'd be like saying "we have $500,000 in the bank at this new restaurant and need to be ready service 5,000 national locations with our staff of 5."
I mean no, by the time that's no longer just a mental exercise (as in you have, say 4,700 locations) you'll be a different kind of institution better able to solve the problem. Literally just forget about it. It's so profoundly irrelevant...
Solve the problems that are actually real, you've got enough of them, I promise.
My general recommendation is to engineer for only 1 order of magnitude greater than you need today, but even that stops applying eventually.
Security and PI stuff is unfortunately something you do have to be super anal about these days but scalability? no.