Are't these denominations synonyms?
They seem so, but on the beginning of the algorithmic trading era, back in 2005-2007, the status quo choose to use the name HFT (or High Frequency Trading) for algorithms that operate faster than a human possibly could. On this article I'll show that what most consider to be "High Frequency Trading" is a misnomer and I'll introduce what appears to be a synonym, "Fast Trading Algorithms", in an attempt to clarify the denomination problem.
Nowadays, circa 2019, High Frequency Trading could better be called "As Fast as Possible Trading" -- AFAPT -- or "Maximum Frequency Trading" -- MFT -- which, not only sounds as cool as HFT, but is also more in sync with the HFT purpose, historically speaking. The reasons why the concept of "High Frequency Trading" is actually "Maximum Frequency Trading" are discussed in more details in the article What really is High Frequency Trading and who should feel threatened by it? -- by now, keep with me only in recognizing that there is a gap between "High Frequency" (or "Fast") and "Maximum Frequency" (or "As Fast as Possible"). We will now dig into those gaps, aiming at differentiating the purpose of the associated algorithms.
When automated trading was introduced (year ~2000) large investment banks and hedge funds went on an obvious race (which they were already doing) on who had the most lucrative pair: methodology and operation. The first algorithms they automated were those they were already familiar with and knew the results -- because they were operated manually -- and, while big companies could afford having humans doing the work machines should be doing, the first algorithms to be automated were the most simple ones -- some departments of those large companies used to create the methodologies and other departments, with cheaper workforce, were tasked to operate them. Back in 2000's, any algorithm automating those methodologies would bring advantages -- time based advantages -- over any human operated methodologies their competitors had. Trivial examples of such methodology are "market making" and "latency arbitrage".
So, the key factors one must keep in mind in really understanding what High Frequency Trading is all about, are, so far:
Now we are at a point in history in which:
The gap between High Frequency Trading and Fast Trading should be clear now:
Now, to conclude, these two kinds of strategies all have their space on the ecosystem: there are advantages both in being the first to react (which is what High Frequency Trading Algorithms do) and in being the only one to notice (which is what Fast Trading Algorithms should do).
If your "Fast Trading" algorithm depends on it being the first to react, you should conclude your strategy is known by many and you'd better consider selling it to a bank or put it in the Hall of Algo Trading Failures.
On the other hand, if you work for a bank and came up with an algorithm which perform slow because much analysis needs to be done, consider testing it in Ogre Robot and quitting your job :)