I think it's quite rare for any company to have exact similar scale and size of storage in stage as in prod.
We’re like a millionth the size of cloudflare and we have automated tests for all (sort of) queries to see what would happen with 20x more data.
Mostly to catch performance regressions, but it would work to catch these issues too.
I guess that doesn’t say anything about how rare it is, because this is also the first company at which I get the time to go to such lengths.
In this case it seems the database table in question seemed modest in size (the features for ML) so naively thinking they could have kept stage features always in sync with prod at the very least, but could be they didn't consider that 55 rows vs 60 rows or similar could be a breaking point given a certain specific bug.
It is much easier to test with 20x data if you don't have the amount of data cloudflare probably handles.
Either way, you don’t need to do it on every commit, just often enough that you catch these kinds of issues before they go to prod.
Cloudflare doesn’t run in AWS. They are a cloud provider themselves and mostly run on bare metal. Where would these extra 100k physical servers come from?
Doing stuff at scale doesn’t suddenly mean you skip testing.
And just because they host stuff themselves doesn’t mean they couldn’t run on the cloud if they needed to.
Their main cost of revenue is these infra costs.