
What is Algorithmic Trading?
A Beginners Guide for DIY Investors The gap between Wall Street and Main Street started shrinking in the early 2000’s but has accelerated since Covid. What used to be the exclusive playground of hedge funds and institutional giants — blazing fast computers, complex trading systems, and algorithms, is now accessible to everyday investors with a decent internet connection, curiosity, and discipline. This shift is not only about access to new tools, but t’s also about a new way of thinking. It is about replacing gut feelings with rules, replacing panic with process, and replacing “hunches” with historical data. Welcome to the world of algorithmic trading. For the DIY investor, algorithmic trading can seem intimidating: lines of code, statistics, probabilities, and AI bots. But the truth is, algorithmic trading is just a fancy term for something quite simple; it’s using predefined rules and data to decide when to buy or sell. This guide is for the self-directed investor who wants to start and understand what algorithmic trading really is, how it works, what tools are out there, the strategies that can be used, and whether it’s worth your time and money. Like all good things in investing, it’s not a magic bullet. But with the right mindset and risk management, it can be a valuable tool in your investing toolkit. What is Algorithmic Trading? Algorithmic trading is sometimes called algo trading or automated trading because of its use of computer programs to follow a set of instructions to place trades. These instructions can be as simple as “Buy when the price moves above the 200-day moving average” or as complex as multi-variable machine learning models reacting to real time market conditions. At its core, algorithmic trading replaces the manual trade, the time when you click “buy” or “sell” with a set of pre-programmed rules that do it for you. Think of it as an autonomous vehicle, but for your portfolio, as you navigate down your investing journey. There are generally two types of algorithmic systems: Rules-based systems: These follow logical steps based on market data. If condition A occurs, then do action B. For example, if the stock moves above its 50-day moving average and volume spikes, buy. This is a very simple example. But as conditional loops become nested and multi variable, they all followed pre-defined steps. AI-driven systems: These use adaptive models and are often powered by machines, learning to find patterns in vast sets of financial data. They don’t just follow rules; they learn and adjust over time. Development in this area has been exploding since 2024 and is rapidly changing Common inputs used in algorithms include: Price trends Trading volume Volatility levels Timing of trades News sentiment Technical indicators like MACD or RSI Whether you’re working with a simple spreadsheet-based system or a sophisticated neural net, the goal remains the same: to make decisions based on data, not emotion. How Does Algorithmic Trading Work? You can think of algorithmic trading like a factory assembly line. It works in stages as each important step builds upon the prior steps to the final product and goal of a well-executed trade. Here’s a breakdown: 1. Market Data Ingestion The process begins by pulling in lots of data. This includes both historical data (used for backtesting and model building) and real time market feeds that drive actual trade decisions. Market data includes prices, volumes, volatility, order book depth, and even news headlines or social sentiment. Some algorithms work off minute-by-minute data; others look at daily or weekly signals. The quality, speed, and reliability of this data stream can make or break your strategy. 2. Signal Generation This is the logic layer, where the sausage is made. It’s where your algorithmic trading strategies interpret the data and generate a buy or sell signal. This can be as simple as a moving average crossover, or as complex as a machine learning model evaluating dozens of variables. For example, a momentum strategy might buy a stock when its price rises faster than a specific threshold over a rolling period (say, 15% over 44 days) and volume exceeds average. 3. Trade Execution Once a trade signal is triggered, the algorithm passes the output to the execution engine. Here, speed and precision matter. The trade is routed through a broker or trading platform, typically via an API, and placed on the exchange. Some systems will use smart order routing to get the best price across multiple venues, while others may break up large trades into smaller chunks to minimize market impact. In high-frequency or intraday trading, fractions of a second in execution time can affect returns. 4. Backtesting and Refinement This is your test lab. Before running a strategy with real money, you’ll test it against years of historical data to see how it would’ve performed under various market conditions. As much as we would like to be true, we must never forget that just because a system performed well in the past doesn’t mean it will work in the future. That’s why good backtesting includes out-of-sample testing, stress scenarios (like 2008 or 2020), periods of slow rising and falling markets and fast rising and falling markets, as well as reasonable assumptions about trade slippage and transaction costs. 5. Ongoing Monitoring and Adjustments Algorithmic trading isn’t “set it and forget it.” Even fully automated systems require monitoring. APIs break. Data feeds stall. Market regimes change. The most successful DIY traders treat their systems like living, breathing tools while refining them over time, adjusting for new conditions, and learning from mistakes. Even the best algorithm is only as good as its ability to adapt. You must want to commit the time to not only developing a system but continually commit to the ongoing maintenance. Popular Algorithmic Trading Strategies for DIY Investors While hedge funds may run hyper-optimized black box systems, most DIY investors benefit from keeping it simple. Here are several algorithmic trading strategies that are both approachable and powerful: 1. Momentum Trading This strategy assumes