and ... you might be justified in that concern. However... after having been in the web space for 25+ years, it's surprising to me how many people have this as a primary concern ("we gotta scale!") while simultaneously never coming close to having this concern be justified.

I'm not saying it should be an either/or situation, but... I've lost count of how many "can it scale?" discussions I've had where "is it tested?" and "does it work?" almost never cross anyone's lips. One might say "it's assumed it's tested" or "that's a baseline requirement" but there's rarely verification of the tests, nor any effort put in to maintaining the tests as the system evolves.

EDIT: so... when I hear/read "scaling is a main concern" my spidey-sense tingles a bit. It may not be wrong, but it's often not the right questions to be focused on during many of the conversations I have.