Kill Switches and Risk Gateways

An algorithm with a bug — a runaway loop that keeps re-sending the same order, a pricing model gone haywire after bad data — can rack up enormous losses or flood the market with erroneous orders in seconds, far faster than a human could notice and intervene manually. A kill switch is a control, either automatic or a single manual button, that immediately halts a strategy and cancels its open orders once a defined danger threshold is crossed: a position size limit breached, a loss limit hit, an unusually high order rate, or a signal that the strategy's own risk checks have failed.

A risk gateway is the infrastructure that makes kill switches enforceable: every order the strategy sends passes through it first, and it checks the order against pre-set limits (max order size, max position, price collars) before allowing it through to the exchange, rejecting anything that violates a limit. Because the gateway sits in the order path itself rather than watching from the side, it can block a bad order before it ever reaches the market, not just after the fact — regulators such as the SEC require broker-dealers providing market access to have exactly this kind of pre-trade risk check in place.