I'm aware of a couple of companies who behave like that - "well, we could increase our user based by an order of magnitude at any point here, so better spring for the order of magnitude more expensive database, just in case we need it."

Feels like toxic optimism.

It's not just about scaling databases, some people are simply unable to assess reasonable limits on any system. A few years ago certain Scandinavian publisher decided to replace their standard industry tools by a single "Digital Experience Platform" that was expected to do everything. After a couple of years they understood it's a stupid idea and gave up. Then later someone in the management thought that since they already spent some millions of euros they should continue anyway. This behemoth is so slow and buggy the end users work at 1/4th speed but everyone is afraid to say anything as the ones who did have been fired. The current PM is sending weekly success messages. It's hilarious. And all because someone once had a fantasy of having one huge system that does everything.

I love the phrase 'toxic optimism'.

I've noticed business people have a different idea of what 'big data' means to tech guys. The business guys think it means a lot of data like the records of a million people which is a lot of data but not the tech guy definition which tends to be data too large to process on a single machine.

Those come out at something like 1GB and 10TB which are obviously rather different.