What if you could guarantee yourself a profitable trade? What would it look like? You’d have to know before even entering the trade that you were going to make a profit. Anyone who could have that kind of edge would exploit it until they no longer could.
While there’s no such thing as guaranteed profit, arbitrage trading is the closest you’ll get. Traders compete ferociously to get the opportunity to enter these types of trades. For this very reason, profits are generally very slim in arbitrage trading and depend heavily on speed and volume per trade. That’s why most arbitrage trading is done by algorithms developed by high-frequency trading (HFT) firms.