Circuit breakers are now more common. The US has them at whole-market level and individual stock level. Somewhat like an API rate limit, there are tiered penalt

Circuit breakers are now more common. The US has them at whole-market level and individual stock level. Somewhat like an API rate limit, there are tiered penalties - the bigger the intraday drop the longer the time-out period. In the worst case the market will be shut down for the day to cool off. This is one reason you occasionally hear about the exchange ‘stopping trading’ of a security. More details here: https://www.investor.gov/introduction-investing/investing-basics/glossary/stock-market-circuit-breakers https://www.investor.gov/introduction-investing/investing-ba...