I used to support a derivatives trading system at a company called Patsystems, so I’ve seen this. Our legacy system could process trade triggers from 4ms to 7ms, but tracing the behaviour of the new system it could do it in 3ms, great. Except every now and then a GC pause would halt order processing for around 50ms. Our customers hit the roof.

Trading systems trigger almost all their orders based on detecting market changes, which you cannot predict. If a symbol hits a price that triggers one of your trades you want that trade in the market ASAP every millisecond matters. Randomly add 50ms on to that and your trading system is out of business. The customers will go elsewhere.

(Sorry, I missed this over the weekend) - I think the issue in this case is you're selling this as a guaranteed 3ms, going down from 4-7ms. If you have to pause for this 50ms GC once every X trades, then you force the GC to happen _after_ the X-1th trade has completed, but you need to provision an extra 15(?) machines to cover the pause. Otherwise, you're not delivering 3ms trades, you're delivering (3 + GCTime/X) ms. It doesn't matter if GC takes 1ms or 1s, you "simply" need to have the capacity to cover the extra GC time.