If you have the choice between "exciting startup" and "big corporate fintech company" then you don't have worry and economic down turns at all. The reality is

If you have the choice between "exciting startup" and "big corporate fintech company" then you don't have worry and economic down turns at all. The reality is that in a turn down turn you aren't choosing among great options. In 1999 software engineers making 100k+ in 1999 (this was a lot more money back then) working for a cool startup ended up working in banks making boiler plate code for ~80k. Most of them were forced out of the industry. If you're in a position to be making choices like you describe than there is no meaningful down turn in your industry. A more likely outcome in the event of a serious is that in 5 years you aren't doing CS related work. Talk to people that have worked in aerospace during various periods of down turn (or any similar industry).