A rule engine turns raw telemetry into decisions without custom code for every case. A rule might say: when a temperature reading from any cold-room sensor exceeds a threshold for more than a few minutes, write the event to a database and call a webhook that pages the on-call technician. Cloud platforms such as AWS IoT Core and open-source tools like Node-RED both expose this pattern.
Rule engines are quick to set up and easy for non-developers to adjust, which is their strength. They become unwieldy when logic needs state across many messages or joins between streams; at that point a stream processing framework is the better tool.
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