Something like that, where I just write a function that spits out a numpy array or something like that and it gets plotted, would be great, but there is one thing Grafana can do and vega-altair, plotly and even matplotlib (*): a UI that allows to select a time interval to view.
So I can freely pan/zoom in/out in time, and only the required part of the data will be loaded (with something like select … where time between X and Y under the hood). So if I look at a single day, it will only load that day, and only if I dare to zoom out too much it will spend some time loading everything from the last year.
(*) yes, you can do interactive things with matplotlib, but you don’t really want to, unless you must…