Do you use downsampling?
On one sensor, I get data every 5 seconds, so that's over 17,000 entries per day, which takes a lot of loading!
I've read the section on downsampling, but it generally means having 2 charts - one with all of the datapoints (for most recent 1 hour), and another which contains the downsampled data (but not the most recent hour).
It would be great if both could be displayed in the same chart.