Wild west times ! It's worth noting, that things changed a lot in trading systems since then. When I started working in this domain (2009), it was pretty crazy

Wild west times ! It's worth noting, that things changed a lot in trading systems since then. When I started working in this domain (2009), it was pretty crazy how unreliable those systems were, on all sides - banks, brokers, exchanges. Frequently you needed to make sure over the phone, what quantities got executed etc. I remember when the Italian exchange was rolling out their systems, at some point we did "tests" on a mix of production and UAT - if my memory is correct, we were just changing IPs to which to connect for order passing to test for the upcoming release, after the market closed. We couldn't just test in their UAT environment, since it was so bugged and half down most of the time. And let's not even talk about Excel spreadsheets with some VBA code that would make chatGPT swear, that were pricing instruments with volumes traded with a lot of zeros. It's very different nowadays, in part thanks to stories like this one. Most things are automated, and there is much less cowboy's attitude. There are mandatory kill switches, a lot of layers of risk / trading activity monitorings (on your side, on exchange side), and really a lot of hard learned lessons incorporated into the systems. That's also part of the reason why people sometime tend to be naive about how hard it is to build a good trading system - the strategies are sometimes now really smart - it's mostly about how to avoid getting killed by something that's outside of usual conditions.