That's very interesting, and definitely an infrastructure many companies should strive for and could learn from. I'm wondering, however, not how problems were

That's very interesting, and definitely an infrastructure many companies should strive for and could learn from. I'm wondering, however, not how problems were handled, but how were they detected - code throwing exceptions is the easy case, the real problem is code running almost correctly, but with slightly wrong outputs. I imagine there could be many different "sensibility" checks implemented, (e.g. no negative prices, no huge jumps price jumps), but in general it appears to be a very interesting and complex problem.