The monitoring goes quiet
A flat graph can mean stable conditions or stale data. Check when the measurement was made, not just when the screen refreshed.
Three clocks do not mean three fresh readings
- 10:00 · sensor
Last new measurement
- 10:05 · collector
Retrieves the stored measurement
- 10:06 · dashboard
Displays a six-minute-old value
Follow three timestamps
A device measures. A collector retrieves. A dashboard displays.
Those can happen at different times. A successful request may return an old value. Show stale or missing data as unknown rather than carrying the last healthy state forward.
Test the notification path too
Sensors, controllers, collectors, alert rules, and delivery services have separate jobs.
An approved end-to-end test should confirm that the intended responder receives the alert. One reachable endpoint does not prove that.
Keep local safety protection separate from remote monitoring. Missing visibility is not permission to bypass controls.
Try it yourself
The last measurement was at 10:00. A collector reads it at 10:05 and the screen refreshes at 10:06. How old is it?
Check your answer
Six minutes. Fresh display does not mean fresh evidence. Define the response to losing each important signal in advance, based on its consequence and available independent observations.