WHY does it exist? Markets are auctions. Whoever sees and acts on new information first captures the edge before prices adjust. Speed literally is the product.
WHY does distance matter? Information travels at (at best) light speed clight≈3×108 m/s (slower in fibre, ≈2×108 m/s). Round-trip time to a server d metres away over fibre:
Microsecond–millisecond latency, huge order turnover, very short holding periods (flat by day-end), and colocation.
The bid–ask spread in market making is
The gap s=Pa−Pb between the maker's sell (ask) and buy (bid) price, captured per round trip.
Formula for market-maker daily net P&L
Πnet=(s−2c+2r)N, with fee c, rebate r, N round trips.
Why does colocation give an edge
Signals travel at ~light speed; sitting metres from the exchange cuts round-trip latency from milliseconds to sub-microseconds, so you act first.
What is a liquidity rebate
A small payment (r) the exchange gives for adding liquidity (posting a resting order that others trade against).
HFT profit model in one phrase
Tiny edge per trade × enormous number of trades.
What is spoofing
Placing orders with no intent to execute to mislead the market — illegal; distinguished from legal cancels by intent.
Why isn't HFT mostly about predicting direction
It harvests structural, microsecond-lived edges (spreads, rebates, arbitrage) that don't depend on long-term price direction.
Round-trip latency over fibre formula
t=2d/vfibre, with vfibre≈2×108 m/s.
Why is HFT profit sensitive to exchange fees
Edge per round trip is s−2c+2r; small fee changes can flip the whole strategy's sign.
Recall Feynman: explain to a 12-year-old
Picture an ice-cream stand where the price of ice cream changes a thousand times a second. You have a super-fast robot standing right at the counter, while everyone else is running from across town. Your robot buys for 10 cents and instantly sells for 11 cents — only 1 cent profit — but it does this a million times before lunch. That penny, a million times, is a lot of money. And because your robot stands closest, it always gets there first. That's HFT: not being smart about tomorrow, just being fastest right now and doing a tiny trick a huge number of times.
Dekho, High-Frequency Trading (HFT) ka matlab hai machine se, microseconds mein trading karna. Yeh koi jyotish nahi hai jo aapko batata hai ki stock kal upar jayega ya neeche — HFT to bas sabse pehle react karne ka khel hai. Market ek auction jaisa hai; jo naye price ko sabse jaldi dekh ke act karta hai, wahi chhota sa faayda utha leta hai. Isliye HFT firms apne servers exchange ke building ke andar hi rakhti hain — isse colocation kehte hain — taaki signal ko door se aana na pade. Formula simple hai: t=2d/v, distance kam to latency kam.
Paisa kaise banta hai? Do main tareeke: market making (bid aur ask dono quote karo, beech ka spreads har round trip pe kamao) aur arbitrage (ek jagah sasta, doosri jagah mehenga — difference le lo). Per trade profit tiny hota hai, maybe ek paisa ka bhi hissa, lekin din mein N = 20 lakh baar karo to Π=(s−2c+2r)N se acche paise ban jate hain. Yahan c exchange ki fee hai aur r rebate — agar aap liquidity add karte ho to exchange ulta aapko thoda paisa deta hai.
Sabse important insight: profit ek product hai, spread × volume. Agar aap spread jyada rakhoge to koi aapse trade nahi karega, N gir jayega, profit bhi. Aur fees (c) itni matter karti hain ki thodi si badhne pe pura strategy loss mein chala jata hai. Isliye HFT firms rebate-capture pe focus karti hain. Yaad rakho SCARF: Spread, Colocation, Arbitrage, Rebates, Fast — bas yehi HFT ka nichod hai.
