I've been poking at prometheus internals lately and I am starting to wonder if histograms need some sort of hyperloglog treatment to improve on buckets. They don't seem like a very accurate solution.
Or tdigest. For the prom use case, i usually prefer ddsketch. Easier to integrate. Tdigest is really complicated.
That said there are definitely interesting work that need to happen on compressing time series histograms for heatmaps. Iirc influx had some interesting work there.
They’ve released it as experimental recently, and we’ve found it to be a massive improvement over the original histograms. It’s still bucket-based at the end of the day, but the exponential bucket layout and sparse representation seems to work really well in practice.