Quote from stock777:
How are your ECN and Supersoes fills fills? They should be immediate.
Some days they are, and some days, like today, I'm experiencing a 1-5 second lag on some smart executions. and this is with size available.
Take a look at this screenshot. This order was sent via smart, all at once, and with plenty of size available on the ask. It should have been executed immediately. Notice the delay after part of my order was sent to supersoes.