I went through this process myself in setting up a self-clearing BD, so I am fully aware of all of the relevant rules and regulations. >Such checks are only as

I went through this process myself in setting up a self-clearing BD, so I am fully aware of all of the relevant rules and regulations. >Such checks are only as good as the imagination of the author. SEC and FINRA regulations require very specific risk checks. One of those involves looking at potential positions if all of your (buy or sell) orders get filled. You have to sum your max potential gross position across all symbols and decide if you will trip a limit. If so you have to halt. This is not imagination; this is codified. If you send an order for 100 shares, you HAVE TO ASSUME they were filled when you send the next order. That's the rule. This was not left to imagination. "Which is all well and good until you have an issue where two independent systems creat a feedback loop. Such problems are only evident 'at scale'." There should be no feedback where the trading engine affects risk check. In fact, the new rules require separate code bases and separate legal entities.