STI is single threadded (as many execution systems are) and it also only publishes quotes every 100ms. I believe that is a system limitation that you are going to be stuck with. I assume you are using the API (automated). If so you can purchase 3rd party data (get quotes from Bloomberg/Activ/DTN) which will be streaming versus every 100ms. That will improve your data and then you can simply execute through the STI API.