Synthetic monitoring is the second pillar of Edge Observability. Instead of waiting for real users to encounter problems, synthetic monitoring uses scripted tests to simulate user interactions with your digital service, proactively and continuously. Think of it as deploying “virtual users” around the world who are constantly checking on your application’s availability and functionality. These synthetic users aren’t real customers, but they perform actions that real customers would – like logging in, searching, adding items to a cart, or completing a transaction – to ensure everything is working as expected.
The key benefit of synthetic monitoring is that it allows you to find issues before your customers do. Because the synthetic tests can run 24/7 (for example, every minute or every 5 minutes from various locations), you might catch a slow page or broken functionality at 2 AM, long before the first customer logs in that morning. Synthetic checks can also cover scenarios that might be infrequent in real traffic but critical – such as a full purchase flow – making sure those paths work whenever someone tries them. In a DevOps context, synthetic tests are often run not only in production, but even after deployments or in staging, as a kind of automated smoke test of user experience.
So how does synthetic monitoring work? Modern synthetic tools provide frameworks to create scripts or recordings of typical user workflows. For instance, you might record a script for “Homepage -> Login -> Search for Product -> Add to Cart -> Checkout” on an e-commerce site. This script can then be scheduled to run periodically using synthetic monitoring agents. These agents are often cloud-based servers (located in different cities or countries to mimic global users) that will execute the script and measure the outcomes. The measurements include response times for each step, success/failure of actions, rendering time for pages, and so on.
One crucial aspect to highlight is the fidelity of synthetic tests. Some simpler synthetic monitors operate by sending direct HTTP requests to your endpoints – for example, pinging an API or fetching a URL – which is useful for basic uptime checks. However, modern web applications (single-page apps, interactive sites) involve client-side logic, dynamic content loading via JavaScript, etc. To truly simulate a user’s experience, you often need to run a real browser environment as part of the test. This is where tools like Selenium come into play. Selenium is a robust open-source framework for automating web browsers. It essentially allows a script to drive a browser (Chrome, Firefox, etc.) the same way a human would – clicking buttons, filling forms, navigating pages – and to validate what happens on the screen.
Why not just use a simple scripting language like Python for synthetic tests? You certainly can write Python scripts to hit a webpage or API, but those will only tell you if the server responded. They won’t catch issues in the front-end rendering or interactivity, because they’re not actually running the JavaScript or building the page. For example, a Python HTTP check might get a “200 OK” from your web server, but a real user might be staring at a blank page because a JavaScript error prevented the page from rendering content. By using a browser automation via Selenium (which can be driven by Python, Java, etc.), you simulate the full user experience – the script loads the page in a browser, waits for it to render, checks if images or dynamic elements appear, and even interacts with them. In essence, Selenium gives you full browser interaction, making it indispensable for high-fidelity synthetic monitoring. (In fact, many enterprise synthetic monitoring tools under the hood use headless browser automation or allow importing Selenium scripts, since it’s the industry standard.)
Capabilities of Synthetic Monitoring: Good synthetic monitoring setups can do quite sophisticated things beyond just “pinging” a site. They can emulate different network conditions (4G mobile speeds vs fibre broadband), run tests from different geographic locations to detect region-specific problems, and even compare performance over time or against competitors. For example, you might run the same page load test from London, New York, and Singapore – if Singapore consistently shows slower performance, that could indicate a need for a nearer data centre or a CDN issue in Asia. Synthetic monitoring can also be used for benchmarking – measuring your app’s performance with and without certain features, or against industry standards (like measuring against Google’s Core Web Vitals thresholds). It effectively gives you a controlled environment to ask “what if” and see how changes impact performance.