Queries per second (QPS) measures database throughput, but it does not reflect how hard MySQL is working. The latter is measured by Threads_running, expressed as a gauge (whereas QPS is a rate). Before discussing Threads_running, let’s consider an analogy:
The image above is a digital instrument cluster from a car. The big circle on the left is the speedometer, and the big circle on the right is the tachometer. Speedometers are familiar to most: they show how fast the car is going.
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