Latency in Trading

Latency is the time it takes for information or an order to travel between two points: from the exchange to your screen, from your click to the broker, or from the broker to the exchange's matching engine. In everyday life a delay of a tenth of a second is nothing. In trading, it can decide whether your limit order is first in line or last, and whether a quote you saw still exists when your order arrives.

Where latency comes from#

Light in fibre travels at roughly two thirds of its speed in a vacuum, about 200,000 km per second. That is why physical distance matters, and why trading firms pay for straighter fibre routes and microwave links between financial centres.

Why latency matters#

Stale quotes#

The price on your screen is already in the past. In a fast market, by the time your market order arrives, the best price may have moved. This is one source of Slippage.

Queue position#

On price time priority exchanges, the first order at a price gets filled first. Faster participants get to the front of the queue. See Fill Probability and Queue Position and Matching Engines.

Reacting to news#

When economic data or company news is released, firms with the lowest latency can trade on it within microseconds, long before any human reads the headline.

The latency race#

High frequency trading firms invest heavily to reduce latency: placing servers in the exchange's data centre (Co-Location), using specialised network cards and kernel bypass software (Kernel Bypass and Low-Latency Networking), programmable chips called FPGAs and microwave networks between cities. Advantages are measured in microseconds and even nanoseconds. See High-Frequency Trading.

Some exchanges push back with speed bumps, deliberate small delays that reduce the value of being slightly faster, and with batch auctions that match orders at intervals rather than continuously.

Does latency matter for you?#

For most retail and swing traders, no, not in the sense of microseconds. You will never win a speed race against professional firms, and you do not need to. What matters for you:

• A stable connection and a reliable platform, especially for stops and day trading.
• Using limit orders so that stale quotes cannot cost you more than your limit price.
• Not trading in the first milliseconds after news, where only the fastest participants have an edge.
• Choosing timeframes where latency is irrelevant, such as hourly or daily charts.

Measuring latency#

Professional firms measure latency at every step with precise timestamps, comparing when an exchange sent a message with when it was received and acted on. See Exchange vs Receive Timestamps and Latency Measurement and Clock Synchronization and PTP. For retail traders, many platforms show a simple ping to the broker's servers.

Frequently asked questions#

What is latency in trading?#

The delay between an event, such as a price change, and the moment you see it or your order reaches the market.

What is low latency trading?#

Trading designed to minimise delays, using co-location, fast networks and specialised hardware. It is central to high frequency trading.

Does internet speed affect trading?#

A stable, low latency connection helps reliability, but for most non professional traders, order type choice matters far more than milliseconds.

Sources#

• Wikipedia, Low latency (capital markets)