I have been trading with IB and RealTick side by side for 3 years and at times in the past IB quote would lag so far behind the quote shown on RealTick for a fast moving stock that there was no way I could trade the stock if IB quotes were all I had. However, IB's quote servers were separate from IB's order placement servers which meant I often (but not always) could still place accurate orders through IB's order servers using the up to date quotes from RealTick. When and if the high volume fast moving markets return, we will find out how well IB's quote servers hold up. Many foreign investors do not like what they see with the USA's politics and have voted with their feet and pulled their money out of the USA never to return. I am getting off the subject, but I think it will be perhaps another 15 years before the USA markets move into the uncharted territory of another great bull market (I remember the 18 years it took after the 73 - 74 bear market), so it could be a while before IB's quote system gets a real stress test.
Catoosa