So a lot of effort goes into producing a site that could be "Facebook scale" if it became necessary. Although since this is difficult (and expensive!) to test, it's likely that some panicked manual intervention will be required if it does take off.
It's really worth asking "what is the cost of scaling" next to "what is the cost of NOT scaling, and what are the chances of it happening?". Is your organisation even able to benefit from rapid scaling - would it be profitable? Or are you going to end up like that luggage company screaming at its customer service reps to work dozens of hours a day?
If your cloud hosting cost goes from free-tier to $100,000/month in one month, and it's real traffic, is your business actually going to be able to pay that invoice?
Is the static overhead of scalability better for your use case than what a normal PC is capable of, which these days can be quite a lot: https://adamdrake.com/command-line-tools-can-be-235x-faster-...
(Been thinking about this since I mentioned the SRCF earlier, which was a single-server host for years: https://news.ycombinator.com/item?id=21741789 )